Check dive?

Considering sharm for next year.

Looked at a couple of website, but not come across the term "check dive"
before?

Previous you just had a chat with the DM who asked when you last dived, what
experience etc and chose a easier dive for the first drive. Now many of the
redsea centres charge extra for a "check dive" - what does this entail? Are
you doing your open water over again?

Is the check dive cost usually for a whole single dive (ie. say a single
shore dive) before you complete xxx day diving, or is it just an extra
charge imposed for something that is carried out during your first dive of
the package (i.e you book 3 days of 2tanks dives - 1 of these is the check
dive - i.e 6 dives total/ or do you get 3 days of 2dive plus an extra check
dive i.e 7 dives total?)