sounds like you are talking about some type of list management, email or direct mail? related to a lead database?
scrubbing the list means 'cleaning' it... typically from old or inaccurate or no-longer-working mail or email addresses...
a supression file is typically a list of names that you DON'T want to mail...aka they could be a list of people who opted out, aka when you email your blast...the file is suppressed and not mailed to.
not positive on appending, unless it's appending (which means 'adding') something to an email address or a file like more information or something.
ETA...ha ha i just googled append email address (btw you can google any of these terms!) and found out that i was pretty much right, it would be if you have name and mail adress but want to 'add' an email address to that person's information file in your database. or vice versa, aka have an email address but no other info on the lead.