Price discrimination is the practice of charging different prices to different customers. Despite the name, the practice is usually legal, as long as it's not discriminating based on race, gender, age, etc. Perfect price discrimination is the theoretical ideal of charging each customer the maximum that they would pay. This is impossible to achieve in practice, although trying to approximate it is a worthwhile goal. Some examples of price discrimination are: hardback and paperback editions of books; "lite" versions of software that include fewer features or lack customer support; premium pricing for faster response; discounts to price-sensitive customers willing to use coupons or rebates; and quantity discounts. Remember that when you price discriminate you become your own competitor and need to be careful that you don't end up encouraging customers who would've paid a higher price to opt for a lower-priced version of your product.