This document summarizes an OER Research Hub report on understanding the impact of open educational resources. It lists 11 hypotheses about how OER can improve student performance and satisfaction, widen participation in education, help at-risk learners, lead educators to reflect on their practice, and bring financial benefits. It also discusses how open licensing is important for educational reuse but that indicators of quality are the most important factor for learners selecting OERs. The document provides initial evidence to support some hypotheses, such as how OER have improved student mastery and pass rates in math courses.