what is the difference between diffusion and osmosis?

In diffusion the solute, I.e the substance that is dissolved, moves from area of its higher concentration to area of its lower concentration. It usually translates to movement is solute from an area if high osmolarity/osmolality(basically concentration) to the area of lower one.

In osmosis it's the movement of water from area of its higher concentration to area of water's lower concentration. What this actually means is that water moves from an area of low osmolarity/lality to the address of higher osmoles to equalise the concentrations. either the membrane/barrier is impermeable to solute, but allows water movement thus only osmosis occurs, or the membrane allows the movement of both the solute and water (solvent and this both osmosis and diffusion occur)
This is the basic difference between the two.

Others are like osmosis is always passive I.e never requires energy, while diffusion may be passive, facilitated(needing transport proteins but not energy) or active, being energy.

Osmosis	Diffusion
It is the movement of water.	It is the movement of solute particle.
Membrane is required	Membrane is not required.
Movement from low concentration to high concentration of solute.	Movement from high concentration to low concentration of solute.
It is associated with liquids.	It is associated with both liquid and gases