Chilli is a fruit which belongs to Capsicum genus. It has many varieties which are differentiated on its pungency measured on Scoville Scale. Chilli fruit when ripened and dried becomes red chilli, which is further grounded to form red chilli powder.
Red chili's are usually grounded into a powder and used as a spice. Red chili's are dried or pickled in order to store them for a long period of time. It is a popular ingredient in most Indian dishes and curries. Red chili's are also used extensively for making sauces which are used to add spice to other dishes.