As others have mentioned, it's called the ternary operator. However, if you didn't know that, it would be somewhat difficult to Google it directly since Google doesn't handle punctuation well. Fortunately, StackOverflow's own search handles punctuation in quotes for exactly this kind of scenario.
This search would yield the answer you were looking for. Alternately, you could search for "question mark and colon in c" on Google, spelling out the name of the punctuation.
