These terms enable combinations of words (i.e. your keywords) to be searched at one time with different results, depending on the Boolean Operator used.
You have to let the computer know when you are searching for a phrase or else it will search your phrase as individual words that may or may not be adjacent in the text.
A phrase is two or more words that need to be together in a particular order to make sense.
For example, United States is a phrase.
To tell the computer to search your words as a phrase, enclose the phrase in quotation marks.
So, to search United States as a phrase, you would type "United States" into the search box.