The Abandonment Rate is the percentage of customers who abandon a process, such as a purchase or registration, before it is completed. This percentage is important for businesses because it shows how many users do not complete the desired actions. Typically, the Abandonment Rate is calculated as the percentage of visitors who started a process but did not complete it. For example, if 100 people try to complete an order, but only 70 do, then the Abandonment Rate is 30%. This means that 30% of users abandoned the purchase process.