What's the difference between lens E mount and lens A mount? Tell me in detail ~ I don't understand this aspect

This is the interface between the lens and the fuselage of a SLR camera. At present, the mainstream interfaces are Nikon, Canon and Sony, and none of them are universal. There used to be many ports in MD42, but now Canon uses EF interface.

At present, most interfaces can use adapter rings, but after adapter, some are out of focus and some cannot focus automatically. In short, different brands have different body and lens interfaces.