Textual cues and visual hints that illustrate to a searcher whether the website being visited has the information they have been searching for.  Almost everyone orients themselves in the upper left corner of a SERP. From there they do a vertical scan down near the left side of the listings to look for information scent in the titles present.

Generally the hint of scent we would be looking for is the search query, bolded and near the beginning of the title. If we pick up scent, then we would probably scan horizontally across the rest of the title and pick up some more information scent from the snippet or description that lies below the title. We start at the top and we work our way down in this fashion.