the process of mining creates the bitcoins, as i understand it.
it's an economy based on processing power.
more
New bitcoins are generated by the network through the process of "mining". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new block). Creating a block is a proof of work with a difficulty that varies with the overall strength of the network. The reward for solving a block is automatically adjusted so that in roughly the first four years of operation of the Bitcoin network, 10,500,000 BTC will be created. This amount is halved each four years, so it will be 5,250,000 over years 4-8, 2,625,000 over years 8-12, and so on. Thus the total number of bitcoins in existence will not exceed 21,000,000. See Controlled Currency Supply.
Blocks are mined every 10 minutes, on average and for the first four years (210,000 blocks) each block includes 50 new bitcoins. As the amount of processing power directed at mining changes, the difficulty of creating new bitcoins changes. This difficulty factor is calculated every 2016 blocks and is based upon the time taken to generate the previous 2016 blocks.
https://en.bitcoin.it/wiki/FAQ#How_a...ins_created.3F