This is a useful distinction made by philosophers of language. It allows for there to be an important difference between using a word, as we normally do, and mentioning it. If you use a word, you are talking about the thing that the word denotes. For example, if you say, "The American government is corrupt," the subject of your speech is the actual American government, out there in the real world. If, on the other hand, you merely mention a word, you are not talking about the thing the word denotes, you are instead talking about the word itself. For example, "The word 'kiss' starts with a pointy letter." In this sentence, you are not talking about anything resembling the meeting of the lips with a surface, you are talking about a symbol in English, which happens to mean something like that.

This can be a useful distinction to make when hate speech is under discussion. For example, it is and should be perfectly allowable for me to say, "'Nigger' is a perfect example of a word that often promotes racial tension." If I were to say, "All niggers are short," this would be bad (although, in an interesting case of self-reference, both of my examples are actually mentions--I am mentioning them as examples of what I could say, rather than actually using them).

The big tipoff in written English that there's a 'mention' situation going on rather than a 'use' situation is the presence of quotation marks. Though sometimes used in other ways (for example, in the previous sentence), any mention should be surrounded by single or double quotation marks, as a way of letting the reader know that that's what's going on.

This can also be a way of getting around the age-old problem of tattle-tails: how to accuse someone of swearing specifically. You can't usually run up to the teacher and say, "Miss Ingle, Johnny just said, 'fuck'!" However, I absolutely hate hearing an exchange like this:
Billy: Miss Ingle, Johnny just said a bad word!
Miss Ingle: What did he say, Billy?
Billy: He said, umm... well... (of course, he can't describe it by its meaning, because little Billy has no clue what it means)
Miss Ingle: Was it a very naughty word?
Billy: I don't know. Mom gets mad at Daddy when he says it, though.
Miss Ingle: I'm going to shut my mouth now, because the author of this dialogue is already being driven crazy by this insipid nonsense.

So, my opinion is that people should always be allowed to mention swear words, so long as they do not use them. I'm still not going to encourage my kids to mention swear words in school, though.

Part of the idea of this node is to allow me (and others, if you wish) to softlink it when talking about words you don't like to use--feel free to use it for this purpose!