This makes the water molecule polarized . This is important because it means that the charged ends of a water molecule are attracted to oppositely charged portions of whatever other molecule it encounters, water or otherwise. We said everything is made up of atoms. Atoms and molecules constantly move around, even in matter which is solid. The more the atoms or molecules are moving around, the more energy the matter has.
Temperature then measures the energy or the movement of the molecule.
As something is heated, its molecules move around faster and so the energy and thus the temperature increases. The heat required to do this is a calorie . Now consider those sticky water molecules. Because they're sticky, it's hard to make them move. Thus it takes a lot of energy.