If you twist your body into the shape of a pretzel, you are showing a lot of flexibility. Flexibility is the ability to bend or stretch.
Lots of things can have flexibility. Pipe cleaners are designed for flexibility. A piece of software can boast flexibility when it can be used in different ways by different people. If you are really busy with school, sports and activities, your schedule won't have much flexibility. Please don't get fixed on one set idea — show a little flexibility and listen to others.