Per Cisco , there are 3 privileges:
•privilege level 0 — Includes the disable, enable, exit, help, and logout commands.
•privilege level 1 — Normal level on Telnet; includes all user-level commands at the router> prompt.
•privilege level 15 — Includes all enable-level commands at the router# prompt
However it is not clear what each level can do on Cisco device. I believe level 15 can do anything on the device. Correct me if I am wrong.
but Level 0 and Level 1, it is not clear what they can do ...