Just as one can be left or right handed, surfers have a favourite pivot foot.
If the surfer puts his right foot at the front of the board, he is said to have a "Goofy" foot position. If, on the other hand, the front foot is the left foot, the surfer is said to have a "Regular" foot position.
In order to find out your front foot, pop up straight with your feet together and your eyes closed. Relax your body. Ask someone to push you firmly in the back so that you fall over forwards. The leg that you instinctively move forwards to avoid falling is your front foot!