Wood skimboards are the lowest cost of the range and are generally used for skimming on flat water. This includes the water formed on sand when a wave breaks onto the shore. As wood skimboards are flexible and heavier than epoxy skimboards - they don't float as well and won't allow you to skim out to the waves, as you might have seen the pros do.
Epoxy skimboards on the other hand, have a lightweight core that is covered with fibreglass and epoxy resin. This makes the skimboard lightweight, strong and also very importantly stiff. These qualities will allow you to skim or slide past the shorebreak out to the waves, but make sure to get a epoxy skimboard that is the right size for you. The board should generally reach up to your sternum (just under your chest).