Sometimes you need to have a sale.  The eCommerce add-on has a nicely configurable discount system to help you with this.

By default, there are three types of discount: free shipping, basic and product specific.  Free shipping lets you pick what kind of shipping customers get for free based on how much they spend.  The basic discount reduces the total cost of the order before shipping by some fixed amount or percentage off.  The product-specific discount type lets you pick which products are discounted.

Since they all look the same, we'll use the product-specific one for instructions.

The details for your discount:

• Handle : the name it will go by in the database.
• Name : what your customers see.
• Enabled : whether or not the discount is available 
• Coupon Code : when the discount is enabled, customers will be prompted to enter the code into a text box.  This is the code they can enter.  If you don't use a code, they just get the discount.

This controls to whom and when the discount is available.  As the dialog says, if you don't enter any dates, it will always be available when it is enabled.  The users and groups will let you pick individual users or entire groups that the discount will be available to.  Obviously, they need to be logged in for it to work.

Here you can choose which products the discount applies to.  You can choose either all, one or more product sets or any combination of individual products.  The discount can be either a percentage off of the price or a fixed amount.