The broadcast formats displayed by your television dictate what sort of signals your television is able to receive and display. The number represents how big the picture will be, and the letter represents the way in which the image is refreshed. Generally, the higher the number, the more clearly it will show up on bigger screens. While progressive (p) formats refresh images twice as often as interlaced (i) formats, most users would not notice a significant difference between the two. 1080i, 1080p and 720p are standards for HDTV, while 480p and 480i are standard definition formats.