Active transport is defined as a process that involves the movement of molecules from a region of lower concentration to a region of higher concentration against a gradient with the use of external energy.
During the process of active transport, a protein pump makes use of stored energy in the form of ATP, to move molecules.
Passive transport:
Passive transport is a type of membrane transport that does not require energy to move substances across the cell membrane.
They move from an area of higher concentration to one of lower concentration.
Osmosis:
Osmosis is passive diffusion.
In osmosis, water moves from high concentration to low concentration through a semi-permeable membrane.
Osmosis does not require energy, i.e. ATP for the movement.
Passive diffusion is the movement of solute from high concentration to low concentration.
They do not require ATP to carry out the movement.