The basic data structure behind most text databases and search engines is an inverted index.

Basically it's a map of words to a list of documents containing that word.

eg {"hello": [1, 2], "world": [1,3,4], ...}

(the numbers are document id's)

So for example, the word 'hello' occurs in documents 1 and 2. 'world' occurs in documents 1,3 and 4.

Doing boolean queries is also really easy with an inverted index. You basically get the document set for each word and then do a union on the sets for an OR query.. or an intersection to do an AND query.

Pretty cool right?