The process of mining cryptocurrencies creates new coins, which is necessary because the blockchain requires enough coins to be available to attract new investors. The generation of new coins is also designed to be stable, which helps keep the price of the cryptocurrency somewhat stable. However, the creation of coins is not meant to go on forever, as this would saturate the market and eventually caue devaluation of the coins.
To keep the value of a given cryptocurrency high, most have been designed with what is known as a mintage cap. This is the maximum supply of the coins, and the level at which no more coins will be created. This is a predetermined number, in the case of Bitcoin it is 21 million coins. That’s all there will ever be. Generally the creation of coins is designed in such a way that the mintage cap isn’t reached for decades. While most cryptocurrencies do have mintage caps, there are some, like Peercoin, which do not have mintage caps.