Your ITB is the band that attaches your tensor facia latae (TFL) muscle to the knee. As the ITB is not actually a muscle, it is not possible for it to become tight.

The TFL is attached to the pelvis and the knee (via the ITB). It is possible to place increased tension through the ITB by moving one end of it away from the other- like pulling on one end of an elastic band if held between 2 fingers.