What does diffusion, facilitated diffusion, osmosis, exocytosis, endocytosis, pinocytosis and phagocytosis all have in common? What makes them all different from each other?
They are all different ways to transport materials across the cell membrane.
Diffusion is used to transport small non polar and non charged particles down concentration gradient.
Facilitated diffusion is to transport small polar or small charged particles down concentration gradient, and this of course requires channel proteins.
Osmosis is to transport water molecules down water potential gradient.
Exocytosis is to transport big molecules like proteins out side the cell. e.g insulin hormone.
Endocytosis is to transport big molecules inside the cell.
When it is a droplet of solution that is taken inside the cell the process is called pinocytosis, like the case of Euglena engulfing a droplet from the pond to take the food in it.
And when the particle is a solid one like a bacterial being engulfed by a white blood cell then the process is called phagocytosis.