Understand the principle before the equipment
Psychrometrics is the study of air and water-vapor mixtures. HVAC professionals use it to understand cooling, heating, humidification and dehumidification.
Relative humidity changes when air temperature changes even if the actual amount of moisture remains the same. Dew point is often a more direct indicator of the air's moisture content.
Air conditioning moves the indoor-air condition by reducing both sensible heat and, when condensation occurs, moisture.