Current SIP Sessions - List of all on-going SIP-sessions.

Registered SIP Users - List of all SIP users currently registered.

Refresh... - The web page shows only static information. To always see the latest information, and to be able to view evolving events, press "Refresh" repeatedly.

Parties - The SIP addresses of the two users participating in the SIP session.

Call ID - Unique ID of the SIP session.

SIP address - SIP address used by the user for the registration.

Registration(s) - SIP address(es) with information of where the user is located.

Read more online:
SIP (Session Initiation Protocol)