What is a resit or retake?
A resit — the usual term in the UK — or a retake, as it's more often called in the US, is when a candidate sits an exam again after a previous attempt. The two words mean the same thing; which you hear depends mostly on where you are.
Resits are governed by rules: who is eligible, how long they must wait, how many attempts are allowed, and how the new result is treated (does it replace the old one, or is it capped?). Managing these fairly and automatically matters at scale. Good exam prep between attempts — targeted revision on weak areas — is what turns a resit into a pass.