While traditional currencies are printed by central banks, bitcoins are “minted” by Bitcoin miners. In this way, bitcoin resembles gold. Like gold, there is only a limited amount of bitcoins out there to find. The original Bitcoin protocol permanently limited the total number of bitcoins to 21 million.
In order to get bitcoins, miners must solve complex mathematical problems that require lots of computing power and time to solve. Also, bitcoins are awarded to miners as a form of payment for carrying out the task of validating bitcoin transactions on the blockchain nodes which they maintain.