Bitcoin
A decentralized digital currency that operates without a central bank or single administrator.
Bitcoin’s supply cap is a hard limit of 21 million coins built into the protocol. No person, company, or government can change it. New coins are created through mining at a decreasing rate, and the last Bitcoin will be mined around the year 2140.
Unlike dollars, which governments can print without limit, Bitcoin's supply cap is fixed at 21 million coins.