Cryptocurrency supply is the predetermined amount of coins/tokens that will be issued of a cryptocurrency. Cryptocurrency supply can be characterized either as fixed or infinite.
A fixed supply means a cryptocurrency is issued in a particular and limited amount.
Bitcoin is issued in a fixed maximum supply of 21,000,000 BTC.
An infinite supply of a cryptocurrency implies an unlimited supply of a coin or a token that can be generated or mined at any time.
ETH does not have any fixed maximum supply and can be produced endlessly.
As a rule, there are three types of cryptocurrency supply: circulating, total and maximum.