At first he made it for a stress-management tool. You would spin it to calm yourself down. It is thus the forerunner of the fidget spinner.
The Pyraminx has 933,120 possible permutations (positions) and the lowest possible number of moves you need to do to solve it is 11 moves. It is simpler than the normal Rubik's Cube, but spinning one side will affect three other sides, meaning that using algorithms is a must in order to maintain already solved sides.
There is also the Tetraminx, which is just a Pyraminx with the corners removed. This of course does not affect the difficulty of the puzzle.