Water is a good solvent because it dissolves more things than any other liquid. As a polar molecule, with a negative charge on the oxygen side and a positive charge on the hydrogen side, water can bind to and dissolve ions and other polar molecules.
When polar things are put in water, most of them dissolve. For example, water and sodium chloride, or table salt, interact so strongly that water breaks apart the ionic forces that hold the sodium and chlorine together. Each chlorine atom is drawn to hydrogen, and each sodium atom is drawn to oxygen.
People often call water the “universal solvent,” but there are a lot of things that water can’t dissolve. Oils can’t be dissolved in water because water molecules are more attracted to other water molecules than they are to oil molecules. This clearly separates the water molecules from the oil molecules, with the less dense oil sitting on top of the water molecules. Non-polar plastics don’t dissolve in water for the same reason. Because of this, there are a lot of shopping bags, cups, gas cans, and bottles made of plastic in the oceans and waterways of the world.