In this chapter, Israel engages in another major battle with the inhabitants of the land.
I think this chapter is relatively straightforward. After destroying several kingdoms in the last chapter, Israel is again faced with an alliance of numerous kingdoms from the promised land who are coordinating together to resist the invaders. Unlike the last chapter, we are not given an account of the LORD's miraculous assistance to Israel. Instead, we are only told that "the LORD delivered them" over to Israel. In this case, it seems like Israel was victorious because they launched a pre-emptive strike, attacking this alliance of nations while they were still gathering together and likely unprepared.
After defeating their armies, the cities are again defenseless and Joshua spends the rest of the chapter stomping around massacring towns. Also, we can see that again, the Israelites plunder all of the towns they conquer, and even most of the city structures were captured, except for Hazor. This basically concludes the story section of Joshua with a final "the land had rest from war", announcing the end of this part of the invasion.
There are a few things worth mentioning.
First, there is the curious incident of Joshua being ordered to destroy all of Jabin's horses and chariots. Horses and chariots were at the core of ancient military power. It is widely believed that the Hyksos, who came to dominate Egypt in the 1700s and 1600s BCE, did so in large part due to their innovations with horse and chariot warfare. Although the Hyksos were largely driven out of power, the significance of horses and chariots remained. A very similar command to this is Deut 17:16, which ordered the future king of Israel to not "multiply horses", which is almost like a command to not build up military power. In my commentary on that chapter I suggested that it was to force Israel to depend on the LORD giving them victory in battle, rather than earning victory through their own strength or power. I think the order in this chapter is similar, to burn the chariots and cut the hamstrings of all the horses, so that Israel might not use them in their own battles.
Second, I think most readers of Joshua are unfamiliar with Israelite geography, so I will try to explain what land is encompassed by verses 16-17. Mount Seir is in the south along the border with Edom (which itself is around the southern extent of the Dead Sea), and Mount Hermon is north of the Sea of Galilee, east of modern Lebanon. The Negev is the southern desert so it fits in with the extent of Mount Seir. The last we had heard of Goshen it was a land in Egypt, but apparently there is also a Goshen in the promised land. I would hypothesize there is some common etymological root that would explain the reuse of this name. Since Goshen was a land of prosperity in Egypt, it probably has a similar connotation here, but beyond that I don't know where it is.
Most of the other names I also don't know (like Mount Halak), but even without knowing I think we already get a sense of what land they have taken. They conquered most of the land west of the Jordan river, from a bit south of the Dead Sea up to Mount Hermon, which lies about 50 miles north of the Sea of Galilee. Lachish is in the center of the promised land, and was conquered in the prior chapter. So it would seem Israel now controls all of the promised land except for the Gazan city-states along the Mediterranean coast and probably some parts of the northwest in the area of Tyre and Sidon.
This is fairly extensive, but astute readers will notice that the lands in v. 16-17 do not include the whole promised land. The original promise included all of the coastal land as well. What this means is that the land might have peace for now, but it is almost inevitable that Israel will engage in further conflicts to move into the western and northwestern parts of the land towards the sea (corresponding to modern Gaza and Lebanon). We will see some of these conflicts when we get to Judges. This is foreshadowed in v. 22 which says that some Anakim remained in the Philistine cities of Gaza, Geth and Ashdod.
Lastly, on a minor note, we are told that the Canaanites had their hearts hardened to fight against Israel (v. 20), just like the heart of Pharaoh was hardened. I'm not really going to talk about this more. See my introduction to Joshua for a deeper look at the morality of the Canaanite wars.