>>4092855>PK-AF>Pentax K-AFI think they mean the same thing. It's the old but good screw-drive autofocus system (pic). It's noisy but reliable. Pentax call their mount the K-mount for some reason. So it's often abbreviated as PK.
Yes the mount will accept any lens that has a PK mount. The oldest ones just do not support most of the auto-exposure modes of the camera.
