Quotation marks serve tons of purposes, but they’re mainly used to separate a direct quotation from the rest of the sentence.
Quotation marks can also be used to designate a word as special in some way. This is super useful for technical terms or words and phrases that are used in a non-standard way.
You can even use them as "scare quotes," which is when you use quotes to indicate that you don't buy into the meaning of the word or phrase. The quotation marks convey a sense of irony or disdain.
Don't forget about titles. Use quotation marks to indicate titles of songs, articles, essays, poems, reports, and short stories.
Got a quote or a title or a special term inside of a quote? Welcome to the single life. Use single quotation marks when you've already used double ones, as in:
Aaron read, "William yelled, 'Sir Frogalot, watch out!' as the arrow hurtled towards him."
Quotations and Other Punctuation
Here's the deal:
Periods and commas go inside the quotation mark. No matter what. (Unless you're British, in which case, we love your accent.)
Placement of question marks and exclamation points depends on the sentence.
If a quotation is part of a sentence that asks a question or makes a strong statement, the punctuation goes outside the quotation mark, like this:
What do you think he meant by "I like you, but I don't like you like you"?
If the quotation itself ends in a question mark or exclamation point, then the punctuation goes inside the quotation mark, like this:
Phoebe yelled, "Watch out for that tree!"