Trap Hands
A hand that is likely to be second-best even if it does hit the flop is called trap hand. Classic examples of trap hands are AJ, AT, KQ, KJ, KT, QJ and QT. These hands might look tempting, but in most cases they should be avoided. For example, if you are in early position and limp in with one of these hands you will probably call if there's a raise. That's a huge mistake. If a player in middle or late position makes a raise, he or she is probably holding a strong hand like AA, KK, QQ, AKs, AQs, AJs or KQs. Consequently, if you're holding one of the trap hands mentioned above you suffer a big risk of being dominated even if you hit the highest possible pair on the flop. You will be reluctant to fold in these cases and the mistake of calling a raise with a trap hand may be an expensive one. Another time to fold is when a player in early position raises and you're holding a trap hand. Once again the risk of you being dominated by a stronger hand is too big.
There are exceptions to the rule that you should throw these trap hands away. If you are sitting in late position and are first to act in the pot, the trap hand may well be worth a raise.