figure skating

They are called the compulsory figures. Compulsory figures were eliminated entirely from international competition after 1990

Short answer is: they're not. In 'figure skating' competition, skaters were required to trace certain 'figures,' for example the figure 8, on the ice. The compulsory figures in international competition were dropped completely after 1990.

Compulsory figure illustrations can be had from the skating federation. They have been largely discontinued in these times simply because they are not very watchable. See the link below for more information on compulsories. However it is interesting to note that the skating federation's floral looking symbol, their "logo", is a design that is compulsory figures that was actually skated and photographed.

Something is compulsory if you have to do it, if you are forced to do it. If you have a choice, it's non-compulsory.