A Boolean search is a type of search allowing users to combine keywords with operators (or modifiers) such as AND, NOT, and OR to further produce more relevant results.
There are FIVE Boolean operators (and the Wildcards).
AND – anytime you use this expression, in capital letters, between two words, your search will find only results that contain all the search terms. For example, a Boolean search could be “hotel” AND “New York”. This would limit the search results to only those documents containing the two keywords.
OR – anytime you use this expression, in capital letters, between two words, your search will find results that contain any of the search terms. This can be useful if your term has several synonyms or individuals who may not be listed individually. In our previous example, you might search for “hotel” AND “New York” OR “Big Apple.”
NOT - anytime you use this expression, in capital letters, between two words, your search will exclude specific words. In our previous example you might exclude the main city with a search string like “hotel” AND “New York” NOT “New York City.”
(…) – Parenthesis in a Boolean search work the same way they do in math. They tell you what to solve first. They most commonly appear around OR search strings. Our example from the OR operator might be better expressed as “hotel” AND (“New York” OR “Big Apple”).
“…” – You have probably noticed that the examples included quotation marks around our search terms. They were used here to draw attention to the words. In a Boolean search, quotation marks serve a specific function, which is to group words together. Without quotation marks the search term New York would find every instance of the word New as well as every instance of the word York. By putting the terms in quotation marks, you are telling the search engine to only find instances of both words together.
* and ? and [...] and ! and - and #– The wildcards are a very important part of Boolean searches. They are called Wildcards because they allow the search tool to find variations on a word. You do not have to enter student, study, studied, students, or any other variation to search for all or some. This list is a brief overview of what each of the wildcards are and what they do.
This table was blatantly stolen from https://support.microsoft.com/en-us/office/examples-of-wildcard-characters-939e153f-bd30-47e4-a763-61897c87b3f4
This short video (Three minutes) demonstrates Boolean operators in action.