The 4:3 mode is the classic television screen and most of the silent period movies were shot in this mode. This means that every four units of a picture width will be three units high while in this mode. Thus, if you take your photos or videos recorded in this mode in 4:3 mode, the photos and videos will be fully reflected on the TV screen.

Presentations on SlideShare look best when designed with a 4:3 aspect ratio. That's why 4:3 aspect ratio is usually the best for presentations that will be used for online marketing or multiple purposes.

Standard aspect ratio used for television; one third wider than it is high (1.33:1)

Aspect ratio of 4:3, it is found with traditional CRT monitors, digital cameras and TVs. 

For every 4 units of width, there are 3 units of height, creating a rectangular shape. 

An image sized at 1024 x 768 pixels or 8 x 6 inches fits a typical 4:3 ratio. 4:3 ("Four-by-Three" or "Four-to-Three") aspect ratio can help to improve your video projects.