This flexibility makes Ethereum the perfect instrument for blockchain -application. But it comes at a cost. After the Hack of the DAO – an Ethereum based smart contract – the developers decided to do a hard fork without consensus, which resulted in the emerge of Ethereum Classic. Besides this, there are several clones of Ethereum, and Ethereum itself is a host of several Tokens like DigixDAO and Augur. This makes Ethereum more a family of cryptocurrencies than a single currency.

2) Pseudonymous: Neither transactions nor accounts are connected to real-world identities. You receive Bitcoins on so-called addresses, which are randomly seeming chains of around 30 characters. While it is usually possible to analyze the transaction flow, it is not necessarily possible to connect the real world identity of users with those addresses.
You don‘t need to understand the details about SHA 256. It‘s only important you know that it can be the basis of a cryptologic puzzle the miners compete to solve. After finding a solution, a miner can build a block and add it to the blockchain. As an incentive, he has the right to add a so-called coinbase transaction that gives him a specific number of Bitcoins. This is the only way to create valid Bitcoins.
Despite bringing a number of benefits, decentralized applications aren’t faultless. Because smart contract code is written by humans, smart contracts are only as good as the people who write them. Code bugs or oversights can lead to unintended adverse actions being taken. If a mistake in the code gets exploited, there is no efficient way in which an attack or exploitation can be stopped other than obtaining a network consensus and rewriting the underlying code. This goes against the essence of the blockchain which is meant to be immutable. Also, any action taken by a central party raises serious questions about the decentralized nature of an application.
The price of bitcoins has gone through cycles of appreciation and depreciation referred to by some as bubbles and busts.[167] In 2011, the value of one bitcoin rapidly rose from about US$0.30 to US$32 before returning to US$2.[168] In the latter half of 2012 and during the 2012–13 Cypriot financial crisis, the bitcoin price began to rise,[169] reaching a high of US$266 on 10 April 2013, before crashing to around US$50. On 29 November 2013, the cost of one bitcoin rose to a peak of US$1,242.[170] In 2014, the price fell sharply, and as of April remained depressed at little more than half 2013 prices. As of August 2014 it was under US$600.[171] During their time as bitcoin developers, Gavin Andresen[172] and Mike Hearn[173] warned that bubbles may occur.
Though transaction fees are optional, miners can choose which transactions to process and prioritize those that pay higher fees.[81] Miners may choose transactions based on the fee paid relative to their storage size, not the absolute amount of money paid as a fee. These fees are generally measured in satoshis per byte (sat/b). The size of transactions is dependent on the number of inputs used to create the transaction, and the number of outputs.[7]:ch. 8
Every transaction is a file that consists of the sender’s and recipient’s public keys (wallet addresses) and the amount of coins transferred. The transaction also needs to be signed off by the sender with their private key. All of this is just basic cryptography. Eventually, the transaction is broadcasted in the network, but it needs to be confirmed first.

If you decide to invest in cryptocurrencies, Bitcoin is obviously still the dominant one. However, in 2017 its share in the crypto-market has quite dramatically fallen from 90 percent to just 40 percent. There are many options currently available, with some coins being privacy-focused, others being less open and decentralized than Bitcoin and some just outright copying it.
Once you bought your cryptocurrency, you need a way to store it. All major exchanges offer wallet services. But, while it might seem convenient, it’s best if you store your assets in an offline wallet on your hard drive, or even invest in a hardware wallet. This is the most secure way of storing your coins and it gives you full control over your assets.
Researchers have pointed out at a "trend towards centralization". Although bitcoin can be sent directly from user to user, in practice intermediaries are widely used.[36]:220–222 Bitcoin miners join large mining pools to minimize the variance of their income.[36]:215, 219–222[120]:3[121] Because transactions on the network are confirmed by miners, decentralization of the network requires that no single miner or mining pool obtains 51% of the hashing power, which would allow them to double-spend coins, prevent certain transactions from being verified and prevent other miners from earning income.[122] As of 2013 just six mining pools controlled 75% of overall bitcoin hashing power.[122] In 2014 mining pool obtained 51% hashing power which raised significant controversies about the safety of the network. The pool has voluntarily capped their hashing power at 39.99% and requested other pools to act responsibly for the benefit of the whole network.[123] c. 2017 over 70% of the hashing power and 90% of transactions were operating from China.[124]
If the private key is lost, the bitcoin network will not recognize any other evidence of ownership;[36] the coins are then unusable, and effectively lost. For example, in 2013 one user claimed to have lost 7,500 bitcoins, worth $7.5 million at the time, when he accidentally discarded a hard drive containing his private key.[82] About 20% of all bitcoins are believed to be lost. They would have a market value of about $20 billion at July 2018 prices.[83]
^ The word bitcoin first occurred and was defined in the white paper[4] that was published on 31 October 2008.[10] It is a compound of the words bit and coin.[11] There is no uniform convention for bitcoin capitalization. Some sources use Bitcoin, capitalized, to refer to the technology and network and bitcoin, lowercase, to refer to the unit of account.[12] The Wall Street Journal,[13] The Chronicle of Higher Education,[14] and the Oxford English Dictionary[11] advocate use of lowercase bitcoin in all cases, a convention followed throughout this article.
Take the money on your bank account: What is it more than entries in a database that can only be changed under specific conditions? You can even take physical coins and notes: What are they else than limited entries in a public physical database that can only be changed if you match the condition than you physically own the coins and notes? Money is all about a verified entry in some kind of database of accounts, balances, and transactions.

Cameron and Tyler Winklevoss, the founders of the Gemini Trust Co. exchange, reported that they had cut their paper wallets into pieces and stored them in envelopes distributed to safe deposit boxes across the United States.[106] Through this system, the theft of one envelope would neither allow the thief to steal any bitcoins nor deprive the rightful owners of their access to them.[105]

Smart contract is just a phrase used to describe a computer code that can facilitate the exchange of money, content, property, shares, or anything of value. When running on the blockchain a smart contract becomes like a self-operating computer program that automatically executes when specific conditions are met. Because smart contracts run on the blockchain, they run exactly as programmed without any possibility of censorship, downtime, fraud or third-party interference.
Ethereum was announced at the North American Bitcoin Conference in Miami, in January, 2014.[9] During the same time as the conference, a group of people rented a house in Miami: Gavin Wood, Charles Hoskinson, and Anthony Di Iorio, a Torontonian who financed the project.[9] Di Iorio invited friend Joseph Lubin, who invited reporter Morgen Peck, to bear witness.[9] Six months later the founders met again in a house in Zug, Switzerland, where Buterin told the founders that the project would proceed as a non-profit. Hoskinson left the project at that time.[9]
NEM — Unlike most other cryptocurrencies that utilize a Proof of Work algorithm, it uses Proof of Importance, which requires users to already possess certain amounts of coins in order to be able to get new ones. It encourages users to spend their funds and tracks the transactions to determine how important a particular user is to the overall NEM network.

Bitcoin mining saps energy, costly, uses more power and also the reward delays. For mining, run software, get your wallet ready and be the first to solve a cryptographic problem and you get your reward after the new blocks have been added to the blockchain.Mining is said to be successful when all the transactions are recorded in the blockchain and the new blocks are added to the blockchain.

Monero is the most prominent example of the CryptoNight algorithm. This algorithm was invented to add the privacy features Bitcoin is missing. If you use Bitcoin, every transaction is documented in the blockchain and the trail of transactions can be followed. With the introduction of a concept called ring-signatures, the CryptoNight algorithm was able to cut through that trail.
Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto[15] and started in 2009[16] when its source code was released as open-source software.[7]:ch. 1 Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services.[17] Research produced by University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[18]