Bitcoin is a digital currency that uses a process called mining to secure its network and validate transactions. Bitcoin mining is a network-wide competition to generate a cryptographic solution that matches specific criteria. When a correct solution is reached, a reward in the form of bitcoin and fees for the work done is given to the miner(s) who reached the solution first.

This reward process continues until all 21 million Bitcoins are circulating. Once that number is reached, the mining process is  expected to cease, and Bitcoin miners will be rewarded through fees paid for the work done.