Why is plasma membrane referred to as selectively permeable barrier

it regulates the movement of substances in and out of the cell

Explanation:

The plasma membrane is called as selectively permeable membrane because it regulates the movement of substances in and out of the cell. It means that the plasma membrane allows some material to pass through it and blocks other materials

It is considered a selectively permeable membrane as it only allows certain organisms to enter inside the cell. This property is important as it easily differentiates between invaders and some molecules.