What is removed by osmosis?

Could you please elaborate on what exactly is removed through the process of osmosis? I understand it involves the movement of solvent particles across a semi-permeable membrane, but I'm curious about the specific substances that are typically eliminated in this biological and chemical phenomenon. Is it primarily water molecules, or could it also involve other small molecules or ions? How does osmosis contribute to maintaining the balance of fluids within living organisms, and what are the potential consequences if this balance is disrupted?