This is a fairly helpful explanation of bitcoin mining. To back up a little, and to put it in non-nerd terms, your computer "earns" (or "makes") bitcoins by, basically, doing math. Because it's an "economy," you have to do a lot more math to "earn" the same amount of money over time; new bitcoins are being "issued," with greater "value" (defined as amount of work), until the system reaches a cap, in the year 2033, when we all live in space. Our guide writes: "Since competition made the difficulty level astronomical, they’ve overwhelmingly joined 'mining pools' that hand everyone a consistent small amount of bitcoins proportional to the amount of power their rig contributes, rather than mining solo until they find a block (which could now take months or years). This is somewhat similar to choosing annuity over lump-sum payments after winning a lottery, except that lotteries pay in actual money."
If you've work really, really hard at it—or really, if you started working hard on it a year or more ago—you can technically live outside of real-world currency systems, buying and trading with vendors for your guns, books, web hosting and legal services—even one lone wedding planner, if you are somehow a bitcoin miner who makes a human connection.