A spinner is a small moving shape that tells someone a website is busy working. It is like a rotating sign that says, “Please wait; I have not finished yet.”
You may see one after pressing a button to load results or send a form. The movement can reassure people that their request was noticed, especially when the wait is not instant.
A spinner does not say how much time is left. Pair it with a short explanation when the task might take a while, and stop it when work ends. The page should also make its waiting state understandable to people using assistive technology.