Promotions is a place to get in touch with your clients through public notices. This notices can include offers, new, updates & etc. It is important to set a correct date for start date and expiration date so the offer would be shown at that range only and be expired afterwhile.
Coupons is a great marketing tool to help with users retention rate. A coupon can offer discount on service user requests for. Coupons just like promotions have expiry date and will disappear from user's menu after that time. Customer needs to enter code of coupon either during trip or save beforehead for later use.