Dew point is the temperature air must cool to for water vapor to begin condensing into liquid water. It is a useful measure of moisture in the air.
Why dew point feels different from humidity
Relative humidity changes with temperature, but dew point gives a more direct sense of how much water vapor is present. A higher dew point usually feels more muggy.
Dew point and condensation
When a surface cools below the dew point, water droplets can form on it. That is why dew, fogged windows, and droplets on cold drinks can appear.
Dew point connects closely with humidity and everyday weather comfort.