Trade discount is usually given to the regular clients who are buying the goods in large numbers. It can be like if you buy 100 numbers we will give you 20 numbers free or buy for Rs.1500/- and get 300/- worth free.
Discount is same to above but will be given for Credit clients like if you pay within one week 15%, within 14 days 10% and more than 21days no discount.
Rebate is like buy for 70/- and pay only Rs65/-.