Question

what is osmosis and diffusion

Answer 1

a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one is called osmosis.
Whereas Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration as a result of random motion of the molecules or atoms. Diffusion is driven by a gradient in chemical potential of the diffusing species.

Answer 2

Moving of substance in higher to lower concentration is called diffusion.
And in respect of liquid is called osmosis.