Diffusion is the spread of liquid or gas particles from an area of high to low concentration, until there is an even distribution.
e.g. spraying Impulse

Osmosis is a type of diffusion where water molecules move from an area of high water concentration (dilute solution) to low water concentration across a semi permeable membrane, until it is Isotonic (equal concentrations)

CASE ONE: ANIMAL CELL
If an animal cell is placed into a beaker of distilled water (100% water), osmosis occurs here because..

CASE TWO: ANIMAL CELL
If an animal cell which contains 99.1% water is put in a solution with 98%, osmosis will occur because..

CASE THREE: ANIMAL CELL
If an animal cell which is 99.1% water is placed in a solution which is 99.1% water, osmosis will NOT occur because..

Passive Transport: the movement of particles from more to less, down a concentration gradient, i.e. no energy needed.
e.g. osmosis and diffusion