At a later date, Person B returns a share to them. And B pays them for the privilege of borrowing the share in the first place.

Person B thinks that it will cost less to buy that share in the future than the money they make from selling the share today, which is why they asked A to lend them the share in the first place. They plan to buy a cheaper share and give that back to A.

A doesn’t care if they get back their original share, they just want to get a share back.

So rather than borrowing it is more like renting?

They get interest from Person B, and when the short contract is up, they can force Person B (or more accurately their broker who passes the price on) to buy a replacement stock, regardless of the price. Alternatively, they can attempt to open another short contract, paying more interest to have continue to borrow the stock. Sooner or later, however, person B is legally and contractually required to to return an identical share to person A.

> when the short contract is up

Options are contracts which expire. A short position is not that, it doesn't have any expiration date.

It can be untenable to maintain that short position forever due to costs, but that's a different discussion.