Esters are functional group with COOR, where R is a methyl group. Polyester is a man made fiber, which is a polymer with esters. Polyester is a very popular yarn these days.
Popular polyester is called terylene and another name for the terylene fiber is dracon.
We have seen earlier that esters are formed when a carboxylic acid reacts with an alcohol. Polymerization reaction can make the ester formed into long chain molecules. It reacts with ethylene glycol that has two OH groups to give an ethylene type ester. The polymerization reaction gives polyester and water. This particular polyester is called terylene.