It's a little confusing because fo how Google implemented some of the operators. The boolean + operator in many cases is used in the same way as AND, but Google originally used it to let users to force a specific word to be present in a search result.
So a search for Fish +Chips was a search for both words, but 'Chips' MUST be present. The equivalent search today is Fish "Chips". It's a little annoying because it requires typing another character, and it it is still not always respected.
