$1 is what was matched in the first set of parenthesis. If there were more sets of parenthesis', then it would be available in $2, $3. Of course there are some execptions to this but no point trying to confuse you more at this point.

Most definitely, the join in that example is not really needed and is probably there just to demonstrate how join could be used. In real life, not calling join is going to be faster than calling join.

Just a tongue-tied, twisted, earth-bound misfit. -- Pink Floyd