UserName is a unique identifier. This is always a user's email address.
Choose a password that is not a dictionary word, that others may easily compromise.
Your telephone that others may use to click to call your name in your online buddy list.
Your mobile phone others will use to right click to call in your online buddy list.
If a user is not active, calls will not route to the devices under this account.
The admin group specified allows extended functionality like, being able to see all voicemail, or add user accounts and view billing information.
A user can have one portal extension. This is for your buddy list and notifications to make sure calls and notifications are correctly routed to the correct device.