... continued from Wednesday
... It is less important to know the precise twelve as to notice the significance of the number twelve itself. ... the number twelve links Jesus' followers to the restoration of Israel...
Who were these individuals? They were ordinary guys, the "salt of the earth." The core disciples seem to be fishermen--Peter and his brother Andrew, James and his brother John (Mark 1:16-20). They may even have been part of a fishing guild in Capernaum, directly on the northern shore of the Sea of Galilee. Jesus tells them he is going to show them how to fish for people. By this Jesus presumably means their mission is going to be to prepare the Jews in Galilee for the arrival of God's kingdom and the restoration of Israel.
John 1 remembers Jesus' first encounter with Andrew, Peter, and Philip being at the river Jordan, as they had all come down from Galilee to see John the Baptist. John says they were from Bethsaida, just north of the Sea of Galilee (John 1:44) and also mentions another follower called Nathaniel.  But Mark seems to picture Peter and Andrew living in Capernaum. It is possible to harmonize these two accounts, but we cannot know for sure. Generally we shouldn't try to mix the gospel accounts because we often end up creating our own story that is different from all the gospel stories themselves.
Matthew is said to be a tax collector. There were different kinds of tax collectors. For example, it is possible that Levi, mentioned in such close proximity to fishing in Mark 1, may have been someone who collected taxes on the fish that the fishermen of Capernaum took in. Alternatively, such men could have been toll collectors, who took money from those traveling from one tax area to another.
These individuals were obviously not liked and everything about the gospel portraits of them supports the notion that they accumulated wealth at the people's expense (e.g., Luke 3:13). They were responsible to give so much to those above them, but they also took their own cut for themselves. Jesus does not resist taxes--that's Caesar's business (Mark 12:17). But he opposed tax collectors getting rich off the people's backs.
We don't know much about the other core followers of Jesus. James the son of Alphaeus, "James the Less" in contrast to James the son of Zebedee, seems to have the same father as the tax collector Levi (cf. Mark 2:14). Perhaps tax collecting was the family business. We think of Thomas because of the tradition in John that he initially doubted Jesus' resurrection (John 20:24-29; cf. Matt. 28:17), but we don't know much more. One named Simon is called "Simon the Zealot" (e.g., Matt. 10:4), which at least raises the possibility that he later participated in the Jewish revolt.
Judas Iscariot is of course the follower of Jesus that betrayed him by telling the leaders of Jerusalem where to find him at night. There is no certainty about the meaning of Iscariot. It may refer in some way to the village or area that his family was from, but we do not know for certain where that was. It is at least possible that it was in the very south, which might suggest Judas also met Jesus as he went to see John the Baptist...
 Later Christian tradition equated him with Bartholomew, but this may simply be the pervasive urge of later interpreters to try to harmonize the biblical accounts, usually done rather credulously.