Answer:
The cell 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. It consists of the phospholipid bilayer with embedded proteins. Cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signaling and serve as the attachment surface for the extracellular glycogalyx and cell wall and intracellular cytoskeleton.\
In easy way:
The cell membrane has tiny holes that control the movement of chemicals in or out of cell.Dissolved substances such as food,oxygen and carbon dioxide can pass through cell membrane.Some harmful chemicals are stopped from entering cell membrane.