re·bate
noun
noun: rebate; plural noun: rebates
ˈrēˌbāt/
1.
a partial refund to someone who has paid too much money for tax, rent, or a utility
Basically, you pay whatever price Newegg has ($56 in this case, minus tax/shipping) and when you get the item you can fill out a form and provide some proof of purchase that will give you some money back (in this case $20).