Zoom meaning the ability to make something distant appear closer. Consumer cameras are sold with a maximum zoom which is supposed to define how much closer. For example a camera might be 40x zoom, 4x optical, 10x digital .
Keeping this in view, what is the optical zoom?
An optical zoom is a true zoom lens, like the zoom lens you'd use on a film camera. They produce much better-quality images. Digital zoom: Some cameras offer a digital zoom, which is simply some in-camera image processing.
What is a 3x optical zoom?
The higher the optical zoom, the better the results. In a still camera, an optical zoom of 10x or more is called a "superzoom" lens. Note that if a still camera is advertised with "10x zoom," that does not necessarily mean optical zoom only. In many cases, the optical is 3x with the additional 7x being digital.
What is the meaning of 20x zoom?
Zooms are meant to bring objects in a picture closer than they actually are. The number, 3x, 5x, 10x etc generally means the amount of magnifications that a particular lens on a camera is capable of performing.