Automatically applied coupons are a great way to offer an indefinite discount to every customer utilizing your online ordering. This will help increase the likelihood of them choosing your direct ordering capabilities over a 3rd party solution.
When you are in a Coupon's configuration, you'll see the Auto Apply checkbox. Once you check this box, each time an online order is placed the coupon will apply.
Reminder: you can only have 1 coupon per order. If you have multiple coupons that are set to auto-apply, the better deal will be applied to the users order.