Coordination between Air Attack/Aerial Supervision Module (ASM) and Tankers and Helos. Ensures separation and coordination of aircraft over a fire.
Think of the VHF AM frequency as the air traffic control frequency over a fire. That frequency is not used to discuss tactics, location of drops or anything similar. The Air Tactics Group Supervisor (Air Attack) is the air traffic controller as well, as the name implies, the one coming up with a tactical plan for the use of air resources. Air Attack is also following traffic on the air to ground - command frequency. Air to ground - tactical is for communication between resources on the ground who are in the vicinity of a planned drop or a series of drops. This is individual aircraft communicating with hotshot crews, engine captains, strike team leaders about such things as the position and effectiveness of water and retardant drops.
Air Attack has a lot of their plates with a lot of radios going on at the same time, including traffic on the local unit net, where dispatch relays all sorts of traffic having to do with resource orders, tanker base logistics, shut down times and ETA's of various air resources.
If you ever get a chance and can drive to a location some distance, but within view of a fire and monitor all the various frequencies you will soon figure out how this all works. You should not place yourself near the fire with a lot of looky lous that can get in way and cause problems for the people on the incident. Ideally, you should be about 10-15 miles from the fire, at a vista point and away from neighborhoods that may have to evacuate. Being this far away allows the best views of aircraft operations. Binoculars are a must. I've done this numerous times and never caused any problems for incident. A camera, preferably a good one, which can be used with telephoto lenses can be fun to capture the aircraft flying over the fire and sometimes making retardant drops. I can't emphasize enough to be far from the fire, your ability to see all of it will certainly depend of the terrain and size of the fire. Don't park on the side of the road that accesses the fire, you will soon find yourself being the object of attention for law enforcement trying to keep traffic moving on fire access roads.