What is the saturation pressure of air and what is its relation to relative humidity?

The saturation pressure occurs when one has the maximum possible water vapor dissolved in the air at a given temperature. In this case, it is said that the air is saturated and this condition is adopted for the calculation of the relative humidity of the same. Taking air at a given temperature, Ta, and a certain vapor pressure, pv, and by adding as much water vapor as possible, saturated air is obtained at temperature Ta and with saturation pressure psat at Temperature (Ta). The relative humidity represents the relation between the partial pressure of water vapor present in the air (pv) and the saturation pressure of the same at the same temperature (psat). UR = 100 * (pv / psat).