What is mining?
There is bitcoin hidden beneath the surface of the earth, and us miners are the ones risking life and limb everyday in different groups, some even take the risk to "mine solo" by themselves without any others, but the payoff for these risk-takers can be much larger because they might find a large amount of bitcoin (say, 25 bitcoin) if they are really lucky and have a lot of crystal methamphetamine that they can smoke to keep on mining. Some folks say it ain't even worth the effort these days, but the mining is in my blood. My daddy mined bitcoins and his daddy did, too!
Seriously, though, wikipedia, google, I bet even bing can help you out more than making your debut here with such a question in such an arbitrary thread. "Bitcoin mining". If you like to live in denial, you'll love it!