When one end of a glass capillary tube that is open at both ends, is dipped in a liquid like water that wets the tube, the liquid level in the tube rises to a certain height above the liquid level in the container, as shown below.
Liquids that don't wet the tube like mercury, do not rise in the tube, but fall below its level in the container.
The phenomenon of rise or fall of liquid in a capillary tube is called capillarity.
