What are the official personas defined by ServiceNow?

[Suggy]

I am looking for official details on different personas mentioned by ServiceNow.

1. Some say ESS user, some say end user, some say business user.

2. Some say ITIL user, some say fulfiller, some say resolver

I am looking for official docs on this. Please share if you have.

[Ravi Kand]

System Administrator
Specialized Administrator
Process User
Approver
Requestor.