Bitcoin is a form of digital currency, created and held electronically. No one controls it. Bitcoins aren't printed, like dollars or euros - they're produced by people, and increasingly businesses, running computers all around the world, using software that solves mathematical problems.

Bitcoin can be used to buy things electronically. In that sense, it's like conventional dollars, euros, or yen, which are also traded digitally. However, bitcoin's most important characteristic, and the thing that makes it different to conventional money, is that it is decentralized. No single institution controls the bitcoin network. This puts some people at ease, because it means that a large bank can't control their money.