When you mine Bitcoins, you are securing the network by confirming transaction. Such process is made by an ASIC miner (look it on ebay) and depending on your hashrate (KH/s, MH/s, GH/s, TH/s), network difficulty, and electricity costs, that will determine what you will earn. For more info, i'd suggest you look into these sites: http://www.pcadvisor.co.uk/how-to/internet/how-mine-bitcoins-generate-money-bitcoin-mining-3515249/     http://www.coindesk.com/information/how-bitcoin-mining-works/

Hope this helps. Somebody correct this, if I'm wrong.