Saturation is a condition of temperature and pressure. You can have any ratio of gas to liquid in the saturated system, and it would still be saturated (even as you mentioned, full gas or full liquid). However, the only way to KNOW you are at saturation is to have some quantity of both. If you've got the same substance, existing in both a liquid AND a gaseous state, in a static condition, you are guaranteed to be at saturation conditions. And heat removed or added at this point would change some of the substance from liquid to gas or vice-versa.
If you have a condition where you are ALL gas, most likely you have some level of superheat (which would be the temperature greater than the saturation temperature for your system pressure). If you have a condition of all liquid, you are most likely at some level of subcooling (which would be the temperature less than the saturation temperature for you system pressure).