It will show you the state of all the sub-factions which can't take towns but are able to spawn massive armies that you can't deal with for a while except with a few tactics at the bottom of the guide.
It can show you the state of all the factions strength although take it with a grain of salt, i'm 99% sure it's by fiefs taken by them not by overall unit power. Starting out necessities -First things first, going to reports then victory progress can show you any armies spawned including unique heros. I'll be providing some good to know knowledge that may help you out.Those who have a question about missing information here, feel free to ask me and I may have information on it to add to the guide.1.
Keep in mind this is from the experience of a long time m&b warband player, if you are new to m&b, PoP probably won't be a player friendly mod to start unless you catch on quickly.