Once used it can be recharged by heating to very high temperatures.
Although this process is usually cheaper than replacing the carbon, the cost of periodic recharging / replacement, does not usually make economic sense for large commercial systems.
It’s main uses are de-chlorination of mains make up water, ozone and hypobromous acid removal, replacement for biofilter (in conjunction with ion exchange) where biofiltration is not practical (such as at low temperatures).
Activated carbon can also be used to remove some discolouration from the water.