What does "N.B." stand for, and does it mean something like "P.S."?

Bonsoir, Mlle Fifi!

N.B. stands for "Nota Bene" (Latin for "note well"); P.S. stands for "Post Scriptum" (Postscript, or addition of a note, usually following a signature).

When there are more N.B.s or P.S.s to the same document, letter, message, etc., they are usually numbered: N.B.1, N.B.2, etc.

I hope this helps!

Thanks.
(I first noticed it in a French email, so I mistakenly thought it was French).

there are Latin, the basis of all romanesques languages of which French is one

And QED stands for quid est demonstratum: or case closed; I proved it.

Latin QED = French CQFD (Ce Qu'il Fallait Demontrer)

This posting will be of some assistance for crossword fans for whom QED is a recurring clue/response.