A stack is a container that supports retrieval by last-in, first-out (LIFO) order. The get and put operations for stacks are usually called push and pop, other operations may include peek and isEmpty. A full description of stacks can be found online here.
According to Apprenticeship Patterns by Bavid H. Hoover and Adewale Oshineye, in order to become a journeyman one must learn to explain their craft to others. This is one apprentices effort to learn these skills.