Proximity operators are useful when looking for a combination of keywords within a phrase or paragraph of text. This is most valuable when a combination of terms must be located close to each other with the text of a document.
The most common ones are:
Use N to find your keywords within x words of each other, and appearing in any order. The word you type in front of the N could be first or second in the combination that's found.
Example: employ* N3 graduat* could find both "employment prospects of graduates" and "graduate employment prospects"
Use W to find your keywords within x words of each other – in the order you typed them into the search box. That is, it will look for these words in combination where the keyword in front of the W appears first, and the keyword after the W will follow it with up to x-1 words in between.
Example: employ* W3 graduat* could find "employment prospects of graduates". It couldn't find "graduate employment prospects" because you asked it to find instances where employ* came first.
Proximity operators have the widest variation in functionality of all search operators. For this reason it is best to go to a database's help page to review how to use these in your search.
Note: If you plan to use any form of proximity search as a part of a high level review, you must ensure that the same types of limiters are used across all databases being searched.