You can configure these by going to Settings->Promotions & Fees.
Specials
A Special is automatically applied when the criteria is met on your lead. To set up a special you will name it, set up time periods, and then select your "rule". For example: Rent 2 qualifying items and get 10% off Rental Total
Fees
Fees are set up similar to Specials. Set up your name, time periods and select your "rule". Example: Rent 1 event get a 5% Fee on Rental Total; this is a good example of a Damage Waiver Fee.
Coupon
A coupon is set up like a Special but you would also need to set a "Coupon Code" which would be needed for this discount to apply. 
Packages
Packages are set up using the Advanced Rule. Here you can set up two specific items to receive a special price or two category items to get the special amount. Example: Rent 1 Concession Item and 1 Moonwalk/Bounce House for a total of $300. 
Common examples
Concession machine is $150 by itself, but $100 if rented with an inflatable. You will want to setup your concession machine price at $150, then create a special that says
Rent 1: (select each inflatable), Get 1 Rental: (select each concession), $50 off.
Now if you also want them to get $50 off for each concession if they rent more than one (say they rent a bounce house and 2 concessions) then you should just change the Get # rentals to 99.