An offer is the specific sales package presented to the customer: what you get, what it costs, on what terms, and why now. An ad's success often depends not on the creative but on the strength of the offer — no beautiful video can save a weak offer.
A strong offer makes value outweigh price and makes action easy: a clear result, a risk-reducing guarantee, and an obvious next step.
The offer depends on positioning
An offer built on wrong positioning won't work. One client spent $6,000 and got no leads — the offer wasn't the problem, the positioning was; after repositioning, just $1,200 delivered results. That's why we usually write the offer in 2-3 variants and test them in parallel in ads.