What do the A and M on the SLR lens mean?

These are two of the four basic exposures of cameras.

M: Full manual exposure mode. How many apertures and exposure time to use are completely up to you, no matter what kind of photos you take.

A: Aperture priority exposure mode. You set an aperture, and the camera will automatically give an appropriate exposure time according to the light at that time.

And:

S: shutter priority exposure mode. You set an exposure time, and the camera will automatically give the appropriate aperture value according to the light at that time.

P: program exposure mode. Aperture and exposure time can be automatically given by the camera according to the situation.

On the lens (also on the fuselage), A and M are AF and MF.

Auto focus is auto focus.

MF stands for manual focusing.

One is the exposure mode and the other is the focus mode, which cannot be confused.