The Book of Joshua relates how Joshua led the Istraelites across the Jordan river, into the Promised Land, and how the Israelites started to take possession of the land,
Chapters 1-12 give an account of the military campaigns of the Israelites in Canaan.
Chapters 13-21 may have been written later; they summarize the distribution of the land among the tribes of Israel.
Chapter 22 recounts how the tribes of Reuben, Gad, and half the tribe of Mannasseh returned to the land they wanted, on the East of the Jordan. This was a bad choice - although the land was good for their herds of cattle, they were cut off from the other tribes by the Jordan, and were among the first tribes to be invaded and deported when the Assyruans came to power.
Chapters 23-24 give the closing years of Joshua's life, and his challenge to the people of Israel to contiinue to serve God.

Joshua 2:1 - Jericho was (and still is) a city on the west bank of the Jordan, just north of the Dead Sea. Archaeologists have uncovered ruins which go back beyond the time of Joshua, to a time before pottery was invented.
Joshua 6:25 - Rahab later married Salmon, one of the leaders of the tribe of Judah. Salmon was the grandson of Aminadab (Numbers 1:7, Ruth 4:18-22, Matthew 1:4-6); their son was Boaz, who married Ruth. Rahab's great great grandson was king David.
Joshua 6:26 - the curse on the rebuliding of Jericho was fulfilled 400 years later, when Hiel the Bethelite rebuilt the town (I Kings 16:34). It is not clear whether Hiel's sons were killed accidentally while construction was in progress, or whether Hiel killed them as a pagan sacrifice (this was sometimes done by the Canaanites and others in the region)
Joshua 9:3-27 - the trick of the Gibeonites : the Gibeonites must have been aware that God had told the Israelites to destroy all who lived in Canaan, but to spare towns outside the region, so they made it appear that they had travelled a long way before reaching the Israelite encampment
Joshua 9:27 - this passage must have been written before the time of king Saul, who renaged upon this agreement and destroyed the Gibeonites
Joshua 11:1 - Hazor was one of the largest cities of the region, situated towards the north and west of the Sea of Galilee, and commanding the whole northern region of Canaan. Hazor is currently being excavated by archaeologists.
Joshua 11:2 - The town of Dor, on the mediterranean coast, has also been discovered and is being excavated. The map in the text-book places Dor as being in the sea - this is an exaggeration; some of the cliffs on which the town was built have been washed into the sea, but much still remains on the coast