Before you start mining Bitcoin, it's useful to understand what Bitcoin mining really means. Bitcoin mining is legal and is accomplished by running SHA256 double round hash verification processes in order to validate Bitcoin transactions and provide the requisite security for the public ledger of the Bitcoin network. The speed at which you mine Bitcoins is measured in hashes per second. 

The Bitcoin network compensates Bitcoin miners for their effort by releasing bitcoin to those who contribute the needed computational power. This comes in the form of both newly issued bitcoins and from the transaction fees included in the transactions validated when mining bitcoins. The more computing power you contribute then the greater your share of the reward.