Use AND to narrow down your search. Combining keywords with AND tells the search engine to bring up results with those keywords e.g. chocolate AND wellbeing. This will help you to narrow down your search to those results that have both your keywords in.
You can add several keywords together using AND, but try not to make the list too long as you may find this narrows down your results too much.
Use OR to combine keywords that are the same or similar. For example, American versus British Spellings.
The word wellbeing could be written as one word, hyphenated or as two words.
OR will allow you to broaden your search, bringing up results for any of the words combined with OR.
Use NOT to narrow down your search. It's useful if you keep on seeing things that are not related to your search. Use with care.