The board has fifteen holes in five rows. Fill fourteen of them with tees and leave one empty. A move is a jump: one tee hops over the tee next to it, in a straight line, into an empty hole. The tee you jumped comes out. You keep going until no jump is left.
Finishing with one tee is the goal. Two left is a good board. Most first tries end with four or five.
If you get stuck, the Hint button shows a jump that can still get you down to one. Or step through the full solution from any starting hole.