Anonymous - An unregistered user, such as an Internet browser, or 'guest account'. Typically only allowed to browse public spaces.
User - Anyone with legitimate credentials has this access level.
Elevated - An elevated level, usually for supervisors.
Manager - As the title suggests, this is a person who can create new user accounts within the department he manages, as well as delete existing accounts within this department, and has executive control over functions related to their department. If their department happens to be 'Security' or 'IT', this position is very powerful indeed.
Security - Anyone with security credentials has this access level, which lets them access practically any physical location in the office, and has moderate network access (typically to disable accounts or reset passwords, or query or disconnect suspicious connections).
Executive - Corporate executives typically have special access that entitles them to privileged storage and system usage as well as general free reign of the system; while not quite administrative access, it's usually pretty close.
Administrator - An administrative level of credentials, for admins who need to reprogram the system, create new accounts or security groups, reboot systems, or do anything that needs doing. Does not necessarily convey physical access privileges.
Root - The holy grail of access; while most operating systems deny this to users and administrators, many enterprising hackers have figured out ways to grant themselves this level of access whether the kernel likes it or not.