[Morgeruat]

a psionic is a character who uses internal energy, unlike a mage, or cleric who draw upon magic, or a god for their powers, psionic characters have a great deal of psychic powers, being able to sense danger, move things with their minds, use telepathy, or even adjust their own bodies to become more like an animals such as growing claws, fangs, etc.

A Kensai is an oriental character, who relies on "the best defense is a good offense" theory, they perfect their use of their swords to such an extent that they don't wear armor, or magical Armor enhancors like magic rings, bracers, etc. It is regarded as a munchkin class due to some special abilities they recieve such as a whirlwind attack (in 1st edition D&D, I'm not sure about 3rd) as well as some Ki (mental energy that oriental characters get) that they can focus to make attacks do ungodly amounts of damage.