?    A question mark  is called a wild card.  In a search, it replaces one character within a word.

• for example:  you can search Sahar?n if you are unsure whether it is spelled Saharen or Saharan (correct spelling).
• a pound sign (#) is used as a wild card if you want to replace 2 or more letters within a word.

*     An asterisk is used for truncation. It is always placed at the end.  It searches for all words that start with the root phrase before the pound sign. The *  represents any number of letters at the end of the word.

• For example, if you want to search variations of a term, or are unsure of spelling:  white-tai* deer 
  will retrieve both white-tail deer and white-tailed deer (correct form)
• This also works well for plurals that have different endings, or for alternate spellings for terms that are spelled differently in other English-speaking countries

And / Or / Not

These are Boolean operators. 

Think of each keyword as having a "set" of results that are connected with it.

These sets can be combined to produce a different "set" of results. 

AND is used to reveal only the documents that have both  ​concepts.. Use AND to narrow your search.

For example.  Below you see the difference in the amount of results that occurs by using the various operators.

The words "HIV' and 'Denialism will both be present in each record.

OR is a connector that allows either word to be present in each record in the results. Use OR to expand your search.

Either 'adolescents' or 'teenagers' (or both) will be present in each record.

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NOT is a connector that requires the first word be present in each record in the results, but only if the record does not contain the second word.

So a search for HIV AND Adolescents OR Teenagers NOT in the United States will remove records that include United States