In this chapter, we are given an account of the territory captured by Israel and the kings who lived therein.
This chapter marks the end of the story of Joshua and the beginning of the bureaucratic section. Having conquered the land, the Israelites must now make an account and an allocation of the land, dividing it amongst their tribes. That is what the rest of Joshua purports to do. As such, this chapter (and the rest of Joshua) contains numerous names and places, lots of borders and rivers and mountains and territories that the Israelites used to designate the various regions being taken from Canaanites and given to Israelites.
For its part, this chapter contains an account of the territories both east and west of the Jordan and a list of the kings defeated by Joshua. I'll start by saying that, in my opinion, knowing most of these locations is not really necessary to have a good understanding of the OT. I believe it is sufficient to have a general understanding of what places Israel conquered. If you are interested in biblical archaeology, this commentary will not be a very good resource because I am not a professional scholar and even though I have read the OT several times, I still don't know where many of these places are. Many locations in the OT have not been positively identified, although usually the larger cities and mountains are well-known. For learning more about OT geography, I think there are some really good maps out there (frequently found in bible appendices) that lay out Israel's borders in different time periods. You can also try looking up locations in Wikipedia (this is what I do when doing research for this commentary), but sometimes Wikipedia only has stub articles, especially for smaller locations.
I think for this chapter, it suffices to know that Hermon is in the north, Halak and Seir are in the south, and everything else is somewhere inbetween. Og and Sihon were kings east of the Jordan, killed by Moses in the book of Numbers, and the rest of the kings were west of the Jordan, killed by Joshua in this book. I would do more research on it, but I just don't think it's all that necessary to know more.
Most of the kings in this chapter were named before, like the king of Jericho and Ai and Hazor. Some of them were not mentioned previously, which implies they were smaller cities that were captured along with their larger, more notable neighbors (for instance, Megiddo is first mentioned here).