Good question Paige!
Laudry listing an ad is including a list all programs (or program fields for brevity) offered on your ad. This alows you to highlight all of your curriculum offerings on one ad.
The benefit of laudry listing is that you don't need to wait until a curriculum is rotated into the schedule to allow for advertising of that program. A potential drawback to laundry listing is that you will not be highlighting any one program, so respondents will call based on their interests, and not necessarily by the program you want to push.