Question about Orion.Sites SWQL table

I see the SWQL table "Orion.Sites" joined to by a lot of queries when looking in the OrionWeb.log files and the SWIS log files.  I don't really understand what this table does, so I guess that is my first question.  What is the point of the "Orion.Sites" table?  What is a "Site" in the context of the Orion SWQL schema?

Since we have 3 distinct Orion environments right now, I can compare the Orion.Sites table in each to try and figure out something about it.  However, I'm now more confused. 

Two of our environments have 7 Additional Pollers (APE's) and one has 2 APE's.  In each of all three environments the Orion.Sites table only has one entry in it.  In two of those three environments, the only entry in their sites table is the last polling engine in that environment.  The 3rd environment shows the primary server as the only entry...  Even though the third environment shows the Primary poller instead of an APE, the "Website" field is still NULL which seems weird since this one does at least have the website on it.  See the screenshots below to see the table contents for each environment.

1 Primary and 7 APE environment 1:


1 Primary and 2 APE environment:


1 Primary and 7 APE environment 2 (This is the one that has the Primary server as it's only entry):


I'm sure this is probably completely normal but since I don't understand this table and its purpose, it just seems really odd to me the way it functions, so I was hoping somebody with knowledge of the schema can explain it to me.  I'm thinking Sites has something to do with the new High Availability feature since I can't recall seeing this table until relatively recently.  That still doesn't explain why sometimes it seems to pick the last APE in the environment to be its only entry and other times it picks the Primary Polling engine to be its only entry.  Very curious indeed...