Gymnasts use chalk on all six
aperatuses. It creates friction between the surfaces of the hands (or the feet, in the cases of floor and vault) and the aperatus, allowing gymnasts to perform their skills with a slightly smaller chance of killing themselves. It also acts as a
buffer to some of the pain caused by swinging, balancing, supporting, and sliding on the hands alone, and it absorbs sweat.
Chalk is an intergral part of gymnastics, it's all over everything. High bar is impossible to do without chalk, rings is equally so. Pommels is a bit painful, and P-bars is pure torture. It's hard to stick a landing on vault and floor. The chalk used in the gym is not the same type as that used in the classroom. It comes in blocks which are broken up and crushed to form a chunky powder.