Boolean ANDs limit your search. BOTH cats and dogs. Boolean ORs expand your search. OR it is looking for an item that includes ANY of the terms you included in your search. Read the search engine's documentation.
All search engines have some type of help included with the system.
This is well worth a few minutes of your time. Once you know if your engine is defaulting to an AND or an OR search, you can structure you query appropriately. But before we move on, let's review.