There are two types of discounts: general discount and membership discount.

general discount applies to a specific course. It is set in Advanced settings in the Pricing tool, General discounts tab:

Metadata fields can also be found in the Metadata tab, where you can define what metadata to send to the payment processing provider. 

You can either set a discount in percents, or set a specific amount in any currency that is used in your environment. 

Another type of discount is a membership discount, which is a type of discount that applies to a specific user group, role, or organization. It is set in the Discounts tab of the main view of a Pricing tool.

For it to apply, make sure that the corresponding setting should be toggled in Advanced settings of a course, learning path, or event (it is by default).

If a user has an overlap of membership discounts, the highest one will be applied. 

You can also disable/enable all existing membership discounts at once, or toggle each one separately.

eCommerce pricing - Discounts tab

A general discount and membership discounts can be active at the same time - they will be summarized.