Which Magento feature allows defining conditions for discounts based on shopping cart contents?

The feature that allows defining conditions for discounts based on shopping cart contents is Shopping Cart Price Rules. This feature enables merchants to create customized promotions for customers based on various criteria such as product types, quantities, or specific items in the cart. For example, a store owner might set a rule that provides a discount if a customer purchases a certain quantity of a product or a combination of products.

Additionally, Shopping Cart Price Rules can be configured to apply discounts either as a fixed amount or a percentage off the total price, giving store owners the flexibility to create varied promotional strategies to encourage sales. These rules are particularly effective for marketing campaigns aimed at increasing average order value or clearing out specific inventory.

The other choices do not relate to discount management based on cart contents. Customer Reviews involve gathering feedback about products, Product Attributes Management deals with the specifications and characteristics of products, and Multistore Setup facilitates the management of different store views and configurations but does not influence discount conditions. Hence, the focus of Shopping Cart Price Rules on discounting based on cart items makes it the clear answer.