The concept is simple: all you need to do is knock six of your opponent's marbles off the game grid...

But you can only move the other player's marbles if you have more than s/he does. And, because moves are diagonal, there are dozens of options for every turn.
The board is hexagonal, with divots in which the marbles rest, and a track around the edge to catch them as they are pushed off connecting the divots are shallow grooves; players push their marbles from divot to divot along these grooves.
These marbles can be used to push your opponent's marbles as well, as long as you "outweigh" them in the direction you're moving. (i.e., three can push two, two can push one, or three can push one. Three can't push three, because you don't outnumber them.)