The searcher allows you to select a website with Latin-only content and search for a word or phrase in it. Why? Many Latin words are also a part of modern English. Thus, search for a priori and you get dictionary definitions, software companies, articles about Kant and other frivolities. By contrast, use this site to search Corpus Thomisticum and you can find out exactly how Thomas would have used the term. Or search Summa Logicae to find out how Ockham would have used it. Useful for any expression where you want to distinguish the medieval from the modern use (e.g. per se, ratio, argumentum ad hominem and so on).
Also includes a search for a single word in Perseus - useful for determining the syntax of a noun or verb.