Backorder
A domain backorder is an order placed in advance to automatically register a currently taken domain the moment it becomes available again. It is not a purchase guarantee: if several people want the same domain, technology and timing decide.
How it differs: unlike a regular registration, a backorder targets a domain that is still taken and only becomes free after its deletion/blocking period.
Example: you place a backorder on "example.de". After the 30-day RGP ends, the service attempts the registration for you.
Further reading: guide