This is probably off-topic and better suited for a linux shell newsgroup, but here's a few pointers:

• what shell is this? (my guess is bash)?
• man (not dog) is your best friend... I don't know what sqlplus does, but "man sqlplus" is likely to tell you. or "sqlplus --help".
• Basic structure of this script is that it sets up a bunch of variables, then it runs sqlplus, then waits for 30 seconds, then emails (man mailx) PRINT-GROUP w/subject "Printfile Delete" and body is the contents of the purge.lst file.