For asynchronous control signals to flops, if they change close to active clock edge, the output of the flop is unknown (metastable). To avoid this scenario there is a recovery and a removal time that needs to be met to avoid this situation.
Removal timing check ensures that there is adequate time between an active clock edge and the release of an asynchronous control signals. It is like hold time for synchronous signal.
Recovery timing check ensures that there is a minimum amount of time between the asynchronous signal becoming inactive and the next active clock edge. It is similar to setup time for synchronous signals.