The word "Now" is used here to mark a break in the main storyline. Here Matthew tells background information about John the Baptist. (See: [[rc://en/ta/man/translate/writing-background]])
This clothing symbolizes that John is a prophet like the prophets from long ago, especially the prophet Elijah. (See: [[rc://en/ta/man/translate/translate-symaction]] and [[rc://en/ta/man/translate/figs-explicit]])
The words "Jerusalem," "Judea," and "the region" are metonyms for the people from those areas. The word "all" is an exaggeration to emphasize that very many people went out. AT: Then very may people from Jerusalem, Judea, and that region" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-hyperbole]])
# They were baptized by him
This can be stated in active form. AT: "John baptized them" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# They
This refers to the people coming from Jerusalem, Judea, and the region around the Jordan River.