One who is a ‘Physical’ or ‘channel’ is one who has their physical body taken over in order for spirits to speak through them. It is sometimes by talking, scribing or by other examples of being overwhelmed by entities from another plane. The act of being a channel is always associated with extreme fatigue. It takes so much from both the channel and the sender that both feel drained from the experience. Helping the world as a channel is such a draining prospect that very few people can maintain this position for very long.
Approach a channel with a clear mind and open eyes, they are a rare bread even amongst Lightworkers.