According the Hewlett Foundation, Open Educational Resources (OER) are "high-quality teaching, learning, and research materials that are free for people everywhere to use and repurpose." Common examples of OER include textbooks, online courses, lesson plans, software, text, audio, and video. With OER, you are free to download, print, share, and adapt without restrictions.
OER gives instructors the right to retain, reuse, revise, remix, and redistribute open textbooks.
Video: OpenOregon. (2015). OER basics [Video file]. Retrieved from https://youtu.be/-O1RftQowCs
College textbooks are expensive. Northwestern undergraduate students are advised to budget $1200 per year for course materials. While tuition and fees are often non-negotiable, textbook costs vary student by student. Studies have shown that textbook affordability can hinder a student's learning experience. Results from national surveys have estimated that 65% of students have decided against buying a textbook because of the cost and 16% have opted for pirated copies from illegal file sharing websites.[1,2] For undergraduate courses, Open Educational Resources, such as Open Textbooks, have been developed and adopted to address this problem.
Graph: United States Government Accountability Office. (2013). Figure 1: Estimated increases in new college textbook prices, college tuition and fees, and overall consumer price inflation, 2002 to 2012 [Graph]. In College textbooks: Students have greater access to textbook information. Washington DC. Retrieved from http://www.gao.gov/products/GAO-13-368
Source: "2016 Student Textbook and Course Materials Survey: Results and Findings," Florida Virtual Campus Office of Distance Learning and Student Services
Yes. Numerous peer-reviewed studies have been published that compare the effectiveness of OER as teaching tools. Generally, the studies conclude that open textbooks contribute to higher test scores, lower failure rates, lower dropout rates, and that both students and faculty are satisfied with their experience using open textbooks.
Video: Research Shorts. (2016). A review of the effectiveness and perceptions of open educational resources as compared to textbooks [Video file]. Retrieved from https://youtu.be/SX0K0hb_xKE
 Senak, E. (2014). Fixing the broken textbook market. Student Public Research Interest Group. Boston, MA. Retrieved from http://www.uspirg.org/reports/usp/fixing-broken-textbook-market.
 The Nielsen Company. (2016). Textbook trends: How U.S. college students source course materials. Insights (blog). Retrieved from http://www.nielsen.com/us/en/insights/news/2016/textbook-trends-how-us-college-students-source-course-materials.html.
 Wiley, D., Bliss, T.j., and McEwen, M. (2013). Open educational resources: A review of the literature. In Specter, J.M. et al (Eds.) Handbook of Research on Educational Communications and Technology (pp. 781-789). (New York, NY: Spinger). doi: 10.1007/978-1-4614-3185-5_63
 This material was created by David Wiley and published freely under a Creative Commons Attribution 4.0 license at http://opencontent.org/definition/.
 William and Flora Hewlett Foundation. "Open Educational Resources: Overview." (2017) Retrieved from http://www.hewlett.org/strategy/open-educational-resources/
 Hilton, J. (2016). Open educational resources and college textbook choices: A review of research on efficacy and perceptions. Educational Technology Research and Development, 64:4, 573-590. doi:10.1007/s11423-016-9434-9