This document provides an introduction to open educational resources (OER). It defines OER as learning, teaching, and research materials that are in the public domain or released under an open license, allowing free access, reuse, repurposing, adaptation and redistribution. OER can be in diverse formats including images, videos, textbooks, course plans and more. The document outlines some basic principles of open licenses, including allowing materials to be reused, redistributed, revised and remixed. It also discusses benefits and challenges of using OER, such as increasing access to education worldwide but requiring an internet connection.