In the standard Tower of Hanoi problem there are three pegs, A, B, and C. On peg A there are three differently-sized disks, the largest at the bottom and the smallest at the top. These disks must be moved to peg C, but there are two constraints: (1) only one disk at a time can be moved, and (2) a disk cannot be placed on top of a smaller disk. There is an interactive version of the task that you can try for yourself here. This online version will also play the solution for you.
The task is a good illustration of means-ends analysis. Clearly, the starting move that would take you closest to the goal state is to move the largest disk to peg C. However, this is not possible due to the two disks on top of it. Therefore, you need to set the subgoal of moving the middle disk, but this is also not possible because of the top disk, and so on.