it depends on what you plan on doing with your snowboard.
"freestyle" is a word which means the board will be more flexible, and are meant to be short
they are for doing tricks and stuff off of jumps
"freeride" means going down the hill straight.
they are usually longer, stiffer boards.
if your not sure what your looking for, rule of thumb is that if your board has its tail on the floor, its nose should come between your chin and eye level.