A "catch-22" is a paradoxical situation from which an individual cannot escape because of contradictory rules or limitations. The term was coined by Joseph Heller, who used it in his 1961 novel 'Catch-22'. An example of a "catch-22" is: "How can I get any experience until I get a job that gives me experience?".

In the book:

If a pilot is deemed insane, they don't have to fly. To be deemed insane, a pilot must request to be evaluated. If a pilot requests to be evaluated, this demonstrates that he must be sane. Therefore, no pilot can ever be deemed insane, and no pilot can get out of flying. That's the "Catch-22" from the book's title.

Other "catch 22" examples:

1. "The office printer is out of toner. You need to fill out a requisition form to request more toner. You don't have any toner to print out the requisition form".

2. "You lost your eyeglasses, so you have to find them. To look for them, you need your eyeglasses".

3. "You haven't been receiving any mail. You call the postal service to ask why. They say they mailed you a letter indicating a suspension in service. You never received the letter, because you're not getting any mail".

More Info: en.wikipedia.org