Most people don’t realize that their own fiat currency (Pound, Euro, Dollar, etc) is created from thin air by so-called central banks. Central banks control and manipulate currencies in collusion with governments.
Crypto-currencies on the other hand are not controlled by any one – especially not governments or central banks. However, the coins are usually generated by the wallets as rewards for miners. It works basically like this: coins are sent from one wallet to another and these are called transactions. Transactions are stored in a public ledger called the blockchain. The blockchain is created by the miners and their reward is a certain amount of coins.
Source: http://blog.gbcoinfoundation.org/do-you-need-mining-help/