If you have been selling the same thing all the time, it probably won't help you a lot, but then again, it might make a suggestion you have not considered.
If you are new, to listing, this could be a huge help in narrowing down the category you want to list in. It gives suggestions and does not FORCE you to list in that category, but eBay says the more accurate (detailed) you can get, gets better search results.
Of course a well thought out group of words in the title bar will be the best since a vast majority of searches are by words, not category. But that is another topic.
I typed in ""Sometime" sheet music" and it brought me to the right era and category to list. It told me to consider 1920's sheet music and in fact it was published in 1925. I tried another and it had repeated success.
What impressed me was the detail it brings up. Previously I do not think I would have had this result. I will use it next time I struggle with a category.
Speaking of search results, if your item has a bar code or "item number" use it. Google Search LIKES that information and your listings is more likely to be found when Google is used and not the eBay search bar.