Search auto-complete tries to match for a search result while users are typing their query. This enables users to move from trying to recall the thing they are searching for to recognizing what it is from the predictive list provided.
As more text is entered in the search field, the list of possible matches narrows. People are much better at recognizing things they have previously experienced than simply recalling them, so auto-suggest acts as a search assistant to speed up the search process and improve the outcome.
