Knowledge is as important as sticky fingers in the thief world. After all, you have to know who is in possession of an item before you start plotting your heist. The peek skill allows you to take a casual glance at someone's inventory without drawing any attention to yourself in the process. After all, simply looking into someone's inventory could be perceived as a hostile action. There is always a chance, however, that you might fail at peeking, drawing even more attention to yourself.