Bitcoin is a new kind of money and payment system. It uses peer-to-peer technology to operate without a central authority or banks. Transactions and the issuing of new bitcoins are carried out collectively by the network. Bitcoin is open-source, nobody owns or controls it and everyone can take part. Through many of its unique properties, Bitcoin allows exciting uses that could not be covered by any previous payment system.
Built into the bitcoin protocol from the beginning was a 21 million limit to the number of coins that will ever be created. Without a limit to the possible number of bitcoins, they would become like fiat money and decrease in value as more and more and more bitcoins were created. With a limit on it, bitcoin should increase in value.