What exactly is a cpmos?

I've been looking up information on a possible lateral promotion for one of my solders, and they say I can if they are working in their MOS or CPMOS. I know CPMOS stands for career progression military occupational specialty, but I can't find in any manual what that would actually mean to me. I don't want to give a yea or a nea until I know what this phrase means and where I might find that definition. Thanks for the help.