Before we go any further, we have to understand what exactly vertical search is. Basically, it's a different way of performing the search process. In a traditional horizontal search, a search engine will search "horizontally" across a broad spectrum of topics no matter what your query is. If you search for "stars", you're going to be searching for a lot of different categories, and you're going get a lot of different results as well. You'll probably see sites about the actual things up in the sky at night, but you'll also see listings about celebrities, design, and even the Dallas Stars professional hockey team.
A vertical search is designed to only search down through one broad topic. So, a vertical search centered on space and space exploration and knowledge will only search "vertically" through sites related to that. You can think of vertical searching like performing a specialized search for a certain topic. The point of a vertical search is to eliminate information that the user will find useless and instead provide more relevant results.
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