Surface tension is the cohesive force found between molecules that are liquid in nature. This cohesiveness forms a level of resistance at the surface of the liquid that is not present in the same degree beneath the surface.
The surface tension of a liquid results in a skin, which resists external forces. Liquid molecules, such as those in water, have a tendency to cling to each other. With no water molecules above them at the surface, they exert stronger clinging tendencies to the molecules below them and to their neighboring molecules around them. This surface tension allows small objects to float upon the surface of the water.