Quotation marks (" ") are used when you want to search an exact phrase of two or more words. For example searching for social media without the quotation marks gives nearly 18 million results (as of August 2020), whereas searching for "social media" with the quotations marks gives 5 million results.
AND is a limiting term meaning that the more words you put with AND, the few results you get.
OR is an expanding term meaning that the more words you put with OR, the more results you get.
NOT is a limiting term meaning that you are telling the search engine to deliberately eliminate keywords.
Image borrowed from Duke Library's research guide page.