A Discount / Promo Code is a code you generate to provide individuals / groups / clubs / companies / sponsors or even the public with a discount on your registration fees.
Discount / Promo Codes are event specific and can be created on the event management page of the event the code is intended to be used for.
You can create as many for each event as you wish, there is no minimum value and they are completely free to create, issue, use or not use.
Each Discount /Promo Code is valid for the amount (monetary or percentage) you determine when you create it. This value is applied each time the (valid) code is used.
If a Discount / Promo Code is created as a one-time use it can be used only one time. If created as an 'X' time use, it'll be valid for the first 'X' number of times it's used.
If a Discount / Promo Code is created with no maximum (usage) value, it can be used, to its stated value while registration remains open or places remain available.