Multimedia learning environments require learners to integrate information across different sources and modalities, which can pose a challenge for some learners. Providing feedback on student responses can be an effective method of guiding learners to achieve a deep understanding of the material. The feedback principle states that novice students learn better with explanatory feedback than with corrective feedback alone. Explanatory feedback provides the learner with a principle-based explanation of why his or her answer was correct or incorrect, whereas corrective feedback merely informs the learner that his or her response was correct or incorrect. The theoretical rationale is that explanatory feedback guides the learner in selecting the appropriate information and consequently reduces the amount of extraneous processing relative to providing only corrective feedback. This chapter reviews evidence for the feedback principle and explores some of the boundary conditions.