Psychrometric charts and tables are graphical and tabular representations of the properties of air-water vapor mixtures. They provide a convenient way to determine the properties of the mixture, such as humidity, enthalpy, and density, based on temperature and humidity ratios. Engineers can use these charts and tables to quickly and accurately calculate the properties of the air in various engineering applications, such as designing air conditioning systems, cooling towers, and humidification/dehumidification systems.