Question

what is importing in plasma membrane function

Answer 1

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 glycocalyx and cell wall and intracellular cytoskeleton.

As stated above, due to its semi-permeable nature it allows substances like carbon-dioxide urea etc. to go out i.e. it "exports" substances out of the cell.

Similarly it allows substances like oxygen, glucose, amino acids etc. to come inside ie. "imports" substances into the cell.

Answer 2

As Harikrat told semi-permeability is an important property of plasma membrane, It regulates the quantity and type of materials moving in and out of the cell, and prevent contents of cell from leaking out.
Plasma membrane has surface receptors for hormones and other cells, which is important for cellular function and change in configurations, which is needed for the survival of the cell.