Agni

From Second Life Wiki

Agni is the name of the system of servers, (agni.lindenlab.com) that hosts the "grid" (or main grid) of Second Life.

Each sim is hosted on one of these servers, (represented as sim###.agni.lindenlab.com). Each server can hold up to 4 sims.

Despite Teen SL sometimes being called the "Teen Grid", it actually resides on Agni as well. The area in which the Teen SL residents are is a large special estate type, which prevents access back and forth between the two. Stagecoach Island was also a separate estate from both Teen SL and the Main Grid (prior to it's move to Active Worlds).