Question

What is the role of cell membrane

Answer 1

it gives the way to meterials to be transferred from inside to outside the cell r vice versa

Answer 2

The cell membrane could be considered the single most important feature of a living cell (with perhaps the exception of DNA/RNA). It's composed of several types of triacyglyerides and other molecules that form a bilayer separating the cell from the extra cellular space around it.
The reason a cell can survive is because it can create the perfect environment (pH and ion concentrations) for the cell machinery to operate to reproduce DNA and the cell itself. The membrane allows the cell to manipulate the ions it brings in and releases, both actively and passively. Without the proper intake of ions and other cofactors, the proteins inside the cell couldn't function.
Cells often have machinery that allows them to interact with other cells ( some of which are located on the membrane to come into contact with other cells. These come into as cells can inject small DNA molecules (plasmids) into other cells, potentially giving them some form of resistance or a helpful gene.
Simply put, everything in life is compartmentalized in some way. The cell membrane is natures way of doing that.