Feature golf is a program form. Its goal is to to write a short program that uses up all of the possible commands in a programming language without including dead code. Every instruction should be executed at least once. It was intended to present new users an overview of all of the commands in a language.
In addition to using up all commands, a restricted Feature golf must present everything that is possible in a language. For example, if you are posting a solution in brainfuck (which supports nested loops and non-instruction comments), a brainfuck post must contain all instructions as well as at least 1 nested loop and non-instruction comment. Also, people should require users to do a specific thing in addition to inclucing all of the commands.