Once you've completed your residency and are working as a physician, you're considered "an attending."
You have a few options after completing residency. You can either go to work or complete a fellowship. People with further training TEND to make more but that's not necessarilly true. A family practice physician who is the owner of a busy, succesful practice in an underserved area may be competitive with a nephrologist who's employed by hospital.
As for career advancement, you have a few options If you are employed by a hospital, your advancement can be working up the administrative ladder. As you get experience you may take on more responsibilities (setting on various hospital boards and such) eventually maybe becoming chief of your division or chief of medicine, or even sitting on the board of directors and such. Depending on the size of hospital, your administrative duties will determine how much time you spend actually being a doctor. However, many doctors find this distasteful and are content to work as a physician. The amount of compensation you get form being in administrative is variable as well vs. what practicing physicians make.
If you go into academic medicine, your advancement is less on experience and more on getting published and getting your name out there. So you might have some young hotshot publish some big time articles and zip up in rank and pay.
In private practice, advancement is essentially more corporate. For example, you may be hired into a private practice group. Eventually your hope is to be asked to become a partner and buy into the group (which means a big bump in your pay, but also your responsibilities).
