Cohesion is the interaction of molecules of the same substance together. By the force of cohesion if two drops of water come together they form one. Water has high rates of cohesion due to hydrogen bonds.
This phenomenon also called surface tension and is what allows small insects to stand on water.
Cohesion along with adhesion of water to the walls of the narrow tube generate what is called capillarity. This allows liquids to ascend inside the narrow tubes. As long as the cohesion is less than the adhesion, the liquid will rise until both forces are equal.
