What does macro lens 20x mean?

It is the current magnification multiplied by 20 times.

There are generally two structures for distance photography lenses. One type of macro photography lens uses a structure with a built-in telescopic lens barrel, and the other type uses a structure that exchanges the front and rear positions of the optical lens group in the lens.

In order to correctly focus on extremely close subjects, macro lenses are usually designed to be stretched longer so that the optical center is as far away from the photosensitive element as possible, and at the same time, at the center of the lens group In terms of design, we must also pay attention to the control of deformation and chromatic aberration at close range. Most macro lenses have a longer focal length than standard lenses and are therefore not entirely suitable for general photography.