What does [sic] mean? Usually in an article that is quoting someone.?

Answer 1

It's Latin for "thus" and is used in quotes to indicate an error to make clear that the error was made by the person being quoted and not by the person reporting the quote.

Answer 2

It means that there is an error in the quotation, and that error was in the original statement. Something like this:
"I think it's important they put there (sic) money where there (sic) mouths is (sic)," John wrote angrily.
There are usually two points to using "sic." One is to show that the error is not the "reporter's," but rather in the original document or statemen (so the audience doesn't believe that the reporting entity is making typos). This gives more credibility to the reporter.
The other (done sometimes in rhetorical or persuasive writing) is to cast a bad light on the original speaker or writer, to blatantly point out that he or she made an error in spelling, speaking, grammar, or usage. (I think lawyers like to use "sic" to quote other attorneys' writen product to get a small jab in on the other side, for example.)

Answer 3

Sic is a Latin word meaning "thus", "so", or "just as that". In writing, it is placed within square brackets and usually italicized — [sic] is to indicate that an incorrect or unusual spelling, phrase, punctuation, and/or other preceding quoted material is how it was written, or quoted.