By looking on wikipedia I found:
A liposome is a spherical vesicle having at least one lipid bilayer. The liposome can be used as a vehicle for administration of nutrients and pharmaceutical drugs. Liposomes can be prepared by disrupting biological membranes (such as by sonication).
Liposomes are most often composed of phospholipids, especially
phosphatidylcholine, but may also include other lipids, such as egg
phosphatidylethanolamine, so long as they are compatible with lipid
bilayer structure. A liposome design may employ surface ligands for
attaching to unhealthy tissue.
About cell membrane
The cell membrane (also known as the plasma membrane or cytoplasmic
membrane) is a biological membrane that separates the interior of all
cells from the outside environment.The cell membrane is selectively
permeable to ions and organic molecules and controls the movement of
substances in and out of cells. The basic function of the cell
membrane is to protect the cell from its surroundings.
It consists of the lipid bilayer with embedded proteins. Cell
membranes are involved in a variety of cellular processes such as cell
adhesion, ion conductivity and cell signalling and serve as the
attachment surface for several extracellular structures, including the
cell wall, glycocalyx, and intracellular cytoskeleton. Cell membranes
can be artificially reassembled.
So the major difference seems to be the presence of "embedded proteins" inside the cell membrane.