This is an interesting question, because it involves a little misdirection.
The basic term is highlight and lowlight is an extension of that.
2. An especially significant or interesting detail or event.
The term is originally from painting, meaning a bright spot in a darker area—in other words, an area of "high light." From Etymonline:
1650s, originally of paintings, "the brightest part of a subject," from high (adj.) + light (n.).
It came to mean something interesting or significant in a figurative sense before being adopted as a literal denotation.
Then, since we had a term for something, the obvious opposite presented itself: lowlight. This term has been figurative for quite a while (Etymonline has no entry for it), but some sources are coming to accept it in its own right:
an unenjoyable or unpleasant part of an event
What the interviewer is almost certainly interested in is a narrative about your successes and failures on the job: what you did well and what you could have done better.