Water is of interest because it will form solutions with many solids. A solution must be a uniform or homogeneous mixture. Water and oil do not form a solution since the mixture in not homogeneous.
Most liquids used by humans are ither aqueous solutions or oil-based solutions.
A solution is a homogeneous mixture of two or more substances. An aqueous solution is a solution where one of the substance is water. When discussing solutions the solvent is the substance that is present in the largest amount and the other substances are solutes. In aqueous solution water is the solvent.