Redemption Grace Period (RGP)
The Redemption Grace Period is a window after a domain is deleted during which it cannot be freely registered. For .de it lasts 30 days according to DENIC; during it, only the last holder or a third party named by them can re-register the domain.
How it differs: length and rules vary by TLD. Not every extension has an RGP in the same sense.
Example: a deleted .de domain shows the WHOIS status "redemption grace period (RGP)". After 30 days without re-registration it becomes free for everyone.
Further reading: guide · related TLD page