Dry and Wet Steam
Steam is classified as wet or dry.
Wet steam contains water droplets suspended in the steam.
Dry steam contains no suspended water droplets in the steam.
As previously mentioned, saturated steam has just enough heat to remain in a gaseous state. If saturated steam has some heat removed, or, the system pressure increases, it will condense proportionately.
Steam that contains water molecules, is referred to as wet steam, or wet unsaturated steam. Steam that contains no water molecules, is referred to as dry steam, or dry saturated steam. Steam tables usually list data based on dry saturated steam values, but dry saturated steam is difficult to produce in a boiler because some water droplets are almost always present.
A typical high-pressure boiler may contain 2-3% water to 97-98% steam, based upon mass. A typical low-pressure boiler may contain 4-6% water to 94-96% steam, based upon mass. Wet steam is sometimes defined as any steam that contains more than 3% water based upon mass, although to be completely correct, wet steam is any steam that contains water, irrespective of how little. Only after removing all moisture within a steam system, can the system be declared truly dry.
Additional Resources
https://en.wikipedia.org/wiki/Superheated_steam
https://en.wikipedia.org/wiki/Steam