What is the difference between pansexual and polysexual?

A pansexual (pan meaning "all"), in terms of sexual orientation, is someone with the capacity to be attracted to someone regardless of their sex, including those who may be transgendered/transsexual/etc.

A polysexual (poly meaning "many"), in terms of sexual orientation, is someone with the capacity to be attracted to many genders, but not necessarily all of them.