KeeLoq is a hopping-code encryption method used in wireless transmitters and receivers. It is a specific rolling-code family, not a generic label for every rolling-code remote.
Each button press sends a new encrypted code based on a shared key and a changing counter. A receiver that knows the same KeeLoq implementation can accept the next valid code and reject a replay of an earlier transmission.
When replacing or matching hardware, confirm that both sides use KeeLoq (or the exact KeeLoq variant listed on the product) and the same frequency. Do not assume a product marked Rolling is KeeLoq, or that KeeLoq remotes work with a different hopping-code receiver.