Beings of the Prime Material Plane are of solid mass, but the description also referes to the "normal" world, in the sense, that for example Humans, Elves, and other beings of non-astral origin originate from. In contrast to Fire Elementals, who are from the Elemental Plane of Fire.
External links[]
Prime Material Plane on the Forgotten Realms Wiki, a wiki for the Dungeons & Dragons campaign setting Forgotten Realms.