On Registration Form -> Payments/Discounts, you can choose what discounts are available through your event.

Automatic Discounts – These discounts will be applied automatically to a registrant if they meet the requirements you specify

Group Discounts – Like Automatic Discounts, these discounts will be applied to groups of registrants when they meet the requirements set

Discount Codes – These discounts will only be awarded when a registrant enters the associated code. You can control what each discount applies to, and if multiple discounts can be used at the same time.