what does this script do?
 

echo "subject, variable1, var2, var3, var4" > test.csv

for file in file*_new.txt; do
echo `tail -1 $file` >> test.csv

done

Firstly, please use [code][/code] tags when showing code for legibility and to keep indentation.

Second, maybe tell us where you are getting lost?

Is there a particular part you are not following?

Your other thread suggests you don't know much about shell scripting. If you want to learn, I'd suggest reading this.