Using the Boolean Operator AND will narrow your search results (i.e. you'll get fewer results). In this case, using AND will retrieve search results containing both keywords globalization and human rights in each result (represented by the center purple zone).
You're doing any search for any specific piece of information! There's a reason this one is the default option.
Using the operator OR will broaden your search results (i.e. you'll have more results). In this case, using OR will retrieve search results containing the keyword globalization as well as results containing human rights, in addition to the results that mention both.
If you have closely related terms, go ahead and use OR.
Ex, college OR university
Ex, teen OR teenager OR young adult
Using the Boolean Operator NOT will narrow your search results, though it's not as strong as AND. In this case, using NOT will retrieve search results containing the keyword globalization but will exclude any search results containing the keyword human rights.
You keep seeing an irrelevant term in your results.
Ex, Graduation rates NOT England