1)
What are "Charashim"?
1.
Radak, based on Targum Yonasan: They are [Malbim ? thick] forests.
2)
What are "Biranos"?
1.
'Rashi': This is like a big Birah (building). Radak ? this is like "Lo l'Adam ha'Birah" (Divrei ha'Yamim I, 29:1).
2.
Malbim: They are fortresses. Also his father built fortified cities, just his father did so in Ashdod and Eretz Pelishtim, and he did so in Yehudah.
