Bitcoin mining is an extensive subject. To begin with, most people who use Bitcoin are not Bitcoin miners. Bitcoin mining is no longer profitable unless you can afford to purchase and run expensive ASIC mining rigs.
The video below can you a quick overview of the mining process.
“What is Bitcoin Mining?” by bitcoinmining.com
The best online explanation of Bitcoin mining is the Bitcoin Mining Guide on weusecoins.com. If you’re interested in becoming a Bitcoin miner, visit bitcoinmining.com for a complete guide to getting started.