The spontaneous conversion of liquid state into gas without heating is called Evaporation.
The common examples of evaporation are drying of clothes, paints on solid articles, dyes on fabrics etc. A liquid that evaporates readily is said to be volatile. Gasoline evaporates quite readily as compare to water without boiling.
Liquid molecules are found in continuous and random motion. A weak Vander Waal force of attractions holds them in a certain volume. Evaporation occurs when high energy molecules at the surface of liquid break away from their neighbors and escape into the gas phase.
Evaporation depends on various factors such as intermolecular force of attraction, surface area , wind speed, humidity or moisture etc.
During evaporation, the escape of high energy molecules lowers the average kinetic energy of the remaining molecules, consequently the temperature of remaining liquid falls down. Thus it is said that evaporation is a cooling process.