A polo shirt , also known as a golf shirt and tennis shirt, is a form of shirt with a collar, a placket with typically two or three buttons, and an optional pocket. All 3 terms may be used interchangeably. Polo shirts are usually made of knitted cloth (rather than woven cloth), usually pique cotton or, less commonly, silk, merino wool, or synthetic fibers. A dress-length version of the shirt is called a polo dress..

source of google: