The margin is the profit (or markup) that a company earns from a sale. A discount is an acceptable amount that can be deducted from a product price.
Discounts can be applied manually to a proposal in an ad-hoc manner, or they can be set up to apply when a particular threshold is met automatically.
For example, you may want to provide a special discount for your customers or promote sales volumes with threshold discounts configured by value or volume, respectively. Let's take the below example, "5% discount on value over $1000" when the proposal value reaches the $1000 threshold, a 5% discount will be automatically applied. This can be overridden still inside the quote if you require.