Idiom: What's the catch?
Meaning Normally catch is a verb meaning to capture or take hold of someone or something, as well as some other related meanings, here, it is a noun . It refers to a hidden problem or disadvantage in what seems like an ideal situation. We use this idiom most often when we are made an offer that seems too good to be true and when we are convinced that the person presenting the offer must be hiding some disadvantage or problem that would make the offer more realistic. For example, if a very expensive luxury car were being sold for half its value, we would certainly ask 'What's the catch?' It's another way of saying "It sounds good, but are there any hidden problems? Example Dialogue 1 A: He said he'd lend me $20,000 to buy a new car, then I'd just pay him back whenever I'm able. B: Whoa! Really? What's the catch? Example Dialogue 2 A: We'll pay you much more than you are making now and you'll get a hefty sign-on bonus plus full paid vacati...