Superheated steam

Superheated steam is a steam at a temperature higher than its vaporization (boiling) point at the absolute pressure where the temperature is measured.

The steam can therefore cool (lose internal energy) by some amount, resulting in a lowering of its temperature without changing state (i.e., condensing) from a gas, to a mixture of saturated vapor and liquid. If saturated steam (a mixture of both gas and saturated vapor) is heated at constant pressure, its temperature will also remain constant as the vapor quality (think dryness, or percent saturated vapor) increases towards 100%, and becomes dry (i.e., no saturated liquid) saturated steam. Continued heat input will then "super" heat the dry saturated steam. This will occur if saturated steam contacts a surface with a higher temperature.