The AutoComplete feature automatically recalls entries you've already made on Web pages. For example, if you've done a search before for "Thomas Jefferson penmanship" in your favorite search engine, and then start to type "th" into the same search engine again, Internet Explorer suggests possible completions starting with the letters T and H. If you had earlier searched for "Thoreau," you'd also see the name as a suggested completion. You can then just start the search by pressing the arrow keys to make the selection, Tab, and then Enter. But here's a question I get all the time: How do I get rid of that there list?
You do it by managing the AutoComplete settings in Internet Explorer.
The Google toolbar, along with other IE add-ons, includes a feature called AutoFill. The AutoFill feature performs a similar role as AutoComplete but is an entirely separate entity.