What is called liner?

Liner is general term for material or object used as lining or protective layer inside something else to protect, insulate, contain, or improve function, with many types depending on application. For example, bin liner is plastic bag lining trash bin, pool liner is waterproof membrane lining swimming pool to hold water, panty liner is thin absorbent pad lining underwear for feminine hygiene, eyeliner is cosmetic lining eyes, liner in clothing is inner fabric lining jacket or bag, drum liner is bag lining drum, pond liner is waterproof membrane for pond. In shipping, ocean liner is large passenger ship. In makeup, lip liner is pencil lining lips. In construction, chimney liner lines chimney. In sports, liner is line drive hit. So liner is called lining material, protective insert, inner layer, membrane, pad, or ship depending on context, but generally liner is called inner protective layer or lining used to line interior of container, clothing, pool, or as cosmetic or hygiene product.