A rebate can mean the same as a discount when it refers to a reduction of the price during a sale but it also means refund. That is money given back after payment has been made. Rebates may be given on tax, rent and utility bills as well as on goods purchased.

A discount is a reduction in the price that you pay in the store. A rebate is when you pay the full price in the store, but then the manufacturer refunds some of the price to you afterwards (e.g., after you mail them proof of your purchase).