The total supply is the total amount of coins that will ever be created. Mining is creating more coins and bootstrapping the network. This process doesn’t continue indefinitely. Most cryptocurrencies have a capped total supply set forth in the genesis block that limit how many coins will ever be created. From a cryptoeconomics point of view, this scarcity makes the coins a valuable resource. For the perspective of miners, it is the point where the block reward stops and network participation will be encouraged by fees and incentives.