I do not understand how/why the following code is used. Please do not simply refer me to the man pages since I have already reviewed them extensively. Thank you.

exit 2 , exit 3, exit 0
I understand the basics of why the exit command is used, but I still don't understand what the significance/meaning of exit 2, exit 3, and exit 0 are.

The creation (and later deletion) of a temporary file
I understand that creation of the temporary file is used to print the contents of the following commands within that file so the grep command can be used to calculate our echoed results that we want, BUT, isn't there a better way to do it so we don't have to create/delete a file?
ls -log "$1" | awk '{print $1}' | grep -v total > $TF
I understand how the first part is piped to the awk, but I do not understand how the awk command is printing only the first column of information.
As far as the "grep -v total" goes, am I correct in that that command basically says to print to screen only those lines within that first column that do NOT contain the word "total"?