For searching anything on the search bar in the frontend, it gets searched by product name, category name brand name, collection name or any text in the description regarding the product. The search results are based on the entire product name and not the initials. For example, a search for "De" instead of "Deo". You will get different search results i.e. the products in which "Du" is either in their product name or description or category or brand. Whereas, in the auto-complete, the search results are listed on the basis of the product initials and not the complete word.
For example, search for "Ti" in the search result, you will get drop-down results but, if you hit enter it will show no products found.
The working of the search drop-down and the search results are different.