Crypto-currency is digital money which has the same properties similar to physical currencies and is an internet based medium of exchange. It uses block-chain at its core. Block-chain is nothing but pages/blocks connected one after another. Block-chain solves the problem of mutual distrust by sharing the records to a network of system, rather than trusting 1 central agency block-chain goes for the majority rule, because of this method it is more secure.
Bitcoin is one of the most popular crypto-currency. On January 2009 a pseudonymous person released the codes to the public. Similar to online banking bitcoins are stored in a digital wallet. It takes more time when you need to transfer bitcoins. Ethereum is one more application of block-chain. A crypto-currency called ether is awarded whenever a smart contract using an Ethereum Virtual Machine (EVM) is executed. Crypto-currency exchanges is done just like stock market exchanges. People buy these coins just to make lots of money. Uses of bitcoin globalized the criminal activities, as government organization can not track any transactions.
Bitcoin mining takes a lot of computing power. Few people started to follow new set of rules to solve this problem and this coin was called bitcoin cash. Companies with no funds to do a project started making their own crypto-currency and sold them to create capital for their projects. Companies started using block-chain in a innovative way for generating coins. ( For example- A coin is generated every time we save certain liters of water.) Common people can also generate bitcoins by getting themselves a system. This system is specifically used to generate bitcoins. These system has a very good probability of guessing the right answer for the problems.