Surface tension is the tendency of liquid surfaces at rest to shrink into
the minimum surface area possible. Surface tension is what allows objects with
a higher density than water such as razor blades and insects (e.g. water
striders) to float on a water surface without becoming even partly submerged.
At liquid–air interfaces, surface tension results from the greater attraction
of liquid molecules to each other (due to cohesion) than to the molecules in
the air (due to adhesion).
There are two primary mechanisms in play. One is an inward force on the
surface molecules causing the liquid to contract. Second is a tangential force
parallel to the surface of the liquid. This tangential force is generally
referred to as the surface tension.