I know about bitcoin, but what is this mining aspect?
Well basically they created a Bitcoin with the idea that is was like any resource you would mine for (gold, oil, gas, etc). There's a finite number of the resource and that helps determine value - in this case not a whole lot of it. Initially in order to get the Bitcoin you had to mine for it. And you would do that by running a computer program that ran some algorithm that would determine if you got a coin or not.
The faster and more powerful the system the more mining it could do and the greater the chance you would get a coin.
But the problem now is that the resource has pretty much all been mined so the chances of getting a coin are slim. Particularly on home system which are slow and underpowered compared to whats out there mining for these coins.