Answer:
There are two types of passive transport, you have diffusion and facilitated diffusion. Another one could be osmosis which is diffusion of water molecules.
Explanation:
Diffusion is solute passing through the membrane from a higher concentration to a lower concentration until it reaches equalibrium. Osmosis is the same as diffusion only it passes water molecules and it uses aquaporins which is a structure in the membrane to help the water pass. Finally you have facilitated diffusion that uses protiens for diffusions but still not using energy and that is why it is passive transport. The type of substance that can be transported are molecules with no charge or non-polar molecules. Lmk if this helps. Sorry in advance if the answer is not clear to understand.
