Answer:
In this case evaporation is just the phase change of sweat from liquid to gas. The body uses this to cool itself. You can sweat up to 4l/hr for short periods and 1L/hr for longer periods. The body also looses water vapor in the air that is exhaled, because it needs to be humidified for your lungs to process it efficiently and the vapor is exhaled. At higher altitudes it can exceed the cooling effects of sweating. This makes evaporation a major contributor to heat regulation.