Where did they come from?

Bitcoin is generated through Bitcoin mining .Bitcoin mining is the process by which new Bitcoin are originated. When you perfom mining, your computer adds new Bitcoin transactions to the block chain and searches for new blocks. A block is a file that has the most recent Bitcoin transactions recorded in it. If you want to earn Bitcoin through mining, be aware that it is a costly and time consuming process.

Bitcoin mining becomes more difficult over time, in order to facilitate limitation on the supply. It is referred to as a “high performance computing problem” and thus is best solved with hardware that is specifically built for that purpose. In order to mine Bitcoin, you have to “solve a block,” and that gets harder as the network of miners grows. Proof of work must be shown for anything to be valid. It is a very competitive endeavor. To help improve the odds for success, miners often form pools, where resources are combined and any yield from the effort is divided.