Widescreen is a video format with a greater aspect ratio than 4:3. Widescreens have long been used in some movies. In the early 21st century it also became very popular for television and other things like Computer monitors.
Widescreen is often used as a nickname for the 16:9 aspect ratio of television screens. This means that if the television screen was sixteen inches wide it would have to be nine inches tall. Most 20th century television screens were 4:3 which means if it was four inches wide it would have to be three inches tall. A widescreen could be any size with the same ratio. For example, a screen could be 32 feet wide and 18 feet tall and still be considered widescreen.