What do you mean by heat of vaporisation? On what factors does it depend?

The quantity of heat required to evaporate a given liquid at constant temperature is known as heat of evaporation or heat of vaporisation. The heat of vaporisation depends on the strength of intermolecular forces within the liquid.
The amount of heat required to evaporate 1 mole of a given liquid at constant temperature is known as molar heat of vaporisation or molar heat of evaporation. For example, the heat of vaporisation of water at 100°C is 40·6 kJ per mole while that of benzene at 80°C is 31 kJ per mole. The relatively high molar heat of vaporisation of water suggests strong attractive forces in liquid water.