1. Texas Education Code, Section 51.451, defines OER as teaching, learning, or research resource that is in the public domain or has been released under an intellectual property license that permits the free use, adaptation, and redistribution of the resource by any person. The term may include full course curricula, course materials, modules, textbooks, media, assessments, software, and any other tools, materials, or techniques, whether digital or otherwise, used to support access to knowledge.
So, Open Access textbooks are just one type of OER.
Open Educational Resources are licensed to allow users with free and perpetual permission to engage in the 5R activities:
Rising textbook prices continue at a rate exceeding tuition and fees, and at a rate that is three times faster than inflation. Open Educational Resources are free of cost.
Bureau of Labor Statistics
Yes. Both student and institutional performance were researched in a multi-institutional study that showed classes that employ OER have lower drop and withdrawal rates than those using expensive commercial textbooks, thus helping students stay on track to graduate. Further, student academic performance in classes using OER has been shown to be the same or slightly improved over classes using traditional commercial textbooks.