What are some types of material suitable for curtains?

Fabric selection (fabric is made from material/s such as cotton, rayon, nylon, silk, etc.) depends on the outcome you desire. If you want curtains for esthetic value, then any fabric you choose can work. If you want curtains for room darkening, then you want to choose a heavy, closely woven fabric that will not light through like denim or velvet. If you want curtains for privacy (blocking view into house/room) any woven cotton or cotton/poly blend will work fine and you'll probably have the largest selection of colors and patterns from which to choose.