Basic search works by examining the text in a group of documents and building an index of their contents. Then a user comes along and queries that index using a particular word or phrase. Sounds as though it’ll do the job doesn’t it? But what if there are millions of documents which contain the same words, how do you know which document(s) have the information you’re looking for and of those, which are the most relevant? That’s where things get a bit tricky.