This publication is the new edition of EDC's popular 2011 guide by the same name, completely revised to include lessons learned over the last decade, including the massive move to online learning during the COVID-19 global pandemic. Drawing on data from 188 countries and nearly 700 publications, this comprehensive guide explores distance education technologies and approaches for pre- and in-service educators, offering the most detailed, global, and up-to-date information on new technologies and on the inputs that are most valuable to ensure that distance education results in meaningful teacher learning.