AND is the default. That is, a search for puch and carburetor returns all messages that contain those words anywhere.QUOTES (") allow searches for phrases. That is, a search for "puch carburetor" returns all messages that contain that exact phrase, with space.
MINUS (-) eliminates words. That is, a seach for puch and -maxi returns all messages that contain puch but not maxi. You can MINUS a phrase in QUOTES, like puch -"maxi sport".
The search engine is not case-sensitive and searches the title, body, and author.