See Genesis 10:19. Also see Deuteronomy 24:22, Hosea 11:8.
See note on Genesis 13:10. The name was changed after the other cities were destroyed (Genesis 19:22). Bela was still used as a name (Genesis 36:32).
That is, the five cities of the plain.
According to others, 'then for 13 years they rebelled' (Bereshith Rabbah 42). According to some, the servitude began immediately after the Tower of Babel (Seder Olam Rabbah 1; cf. Shabbath 11a, Rashi ad loc. s.v. Esrim).
|had come together|
That is, the kings of Sodom and its sattelites had made a treaty to serve Chedorlaomer, and this treaty was made in Siddim Valley (Rashi). Others say that the five cities of the plain had made a mutual defense pact in this valley. Another possible explanation is that they gathered for war in Siddim Valley (see Genesis 14:8).
After the destruction, this area was submerged to become the Dead Sea. The name Siddim is from the root sadad (cf. Isaiah 28:24, Hosea 10:11), which is also the root of the word sadeh, a field (Radak). Hence, Onkelos translates it, 'Field Valley,' or 'Valley of Fields.' Targum Yonathan renders it, 'Orchard Valley,' but, since the word for orchard is pardes, it can also be rendered 'Paradise Valley' (see Bereshith Rabbah 42).
Yam HaMelach in Hebrew, literally the Salt Sea. In Moses' time, Siddim Valley was no longer known, and it had to be identified. This plain was in what is now the southern part of the Dead Sea, which is much shallower and more recent geologically than the northern part.