Economists typically divide price discrimination into three broad types, known cleverly as 1^st, 2^nd and 3^rd degree price discrimination. More usefully:

1^st degree - perfect price discrimination: Impossible without psychic abilities or Psychic Cash Registers® and psychic vending machines®. It means charging each customer a different price, the maximum they would ever pay. This is what auto salespeople and realtors attempt to do.
2^nd degree - quantity discounts or nonlinear pricing: Different per unit price depending on how much is purchased, relatively common.
3^rd degree - group customers according to demand elasticity: Most common form. All the examples on the prior page and that we will consider here are of this type.