DRY BULB - This is the actual temperature of the air the room.
DEW POINT - This is the temperature where water vapor starts to condense out of the air. When the dew point and the dry bulb are close together - the relative humidity will be high. When the dew point is well below the dry bulb the relative humidity is low. Dew point should always be below the dry bulb or...you will have rain in your room!