A membrane is a thin, selective barrier that separates substances or environments. There are various types, each serving specific functions. Biological membranes, found in cells, regulate the passage of molecules. Synthetic membranes, like those in water filtration systems, remove impurities. Semi-permeable membranes permit only certain molecules to pass through. Additionally, gas separation membranes selectively allow gases to permeate. Membranes can be made from materials like cellulose, polymers, or ceramics, tailored to desired properties. Their applications range from biomedical devices to industrial processes, making them crucial in fields like healthcare, environmental protection, and manufacturing. These versatile barriers play pivotal roles in diverse sectors, ensuring efficiency and sustainability.