What does this short message sent to me by JD.COM mean?

This is just one of their activities. Generally speaking, 79 yuan can only buy its own products, but if you buy something within 79 yuan after this free coupon, you can save the postage (5 yuan is the basic freight, if you want to go to Tibet in a remote area, Qinghai will give you the postage and send it to 5 yuan). I remember that a website called Dragon What 30 is still issuing their coupons, 99- 10.