What is osmosis

Let's say you have a bowl of water and you separate it into two compartments with a partially permeable membrane. This membrane does not allow proteins to pass through but it allows water to diffuse freely. In this situation, solutes attract and keep more water on their respective subcontainer. This event is called osmosis.

What is important to remember about osmosis is that, since it doesn't need ATP, it is a passive type of transport.