The easiest way to search for terms next to each other is to enclose them in quotation marks, also known as phrase searching. For example, "global warming."
Why Use Phrase Searching?
Different databases interpret searches differently. Some databases assume that two words next to each other should be searched as a phrase. Some databases will put a boolean operator AND between two words.
For example, if you were to look for "global warming" in a database, that database will interpret that search in one of two ways:
"global warming" as a phrase, or
"global AND warming", which might not be what you intended.