This document provides a literature review and overview of augmented reality (AR) technologies. It discusses several enabling technologies for AR, including head-mounted displays, handheld displays, and tracking methods. The document reviews research on AR development tools, applications of AR in education, and challenges and future directions for AR. Key advantages of AR include enhancing real-world experiences and making invisible objects observable. However, challenges include cognitive overload and usability difficulties for some users. Overall, the literature indicates that AR has significant potential to improve education and other fields when designed appropriately.