This report analyzes findings from research into online learning in order to provide guidelines for further research and practice. within this tertiary study, we performed a systematic review of thirty-two second-order studies that address issues of teaching and learning in online settings. From the examination of the studies included in the review, four prominent topics emerged: i) comparison of online learning with the traditional classroom, ii) comparison of various instructional practices within two or more online courses, iii) perspectives of students and instructors regarding learning and teaching in online settings, and iv) adoption of online learning in institutions of higher and adult education. except for showing no significant difference in effectiveness of online learning compared to traditional face-to-face settings, the studies within the first theme also provided directions for further research, necessary to better understand what practices work best in online settings. Our findings further indicate that contemporary research into online learning almost univocally agrees that structured online discussions with clear guidelines and expectations, well-designed courses with interactive content and flexible deadlines, and continuous instructor involvement that includes the provision of individualized, timely, and formative feedback are the most promising approaches to fostering learning in online environments. however, this also implies a more complex role for the instructor in online settings, and a need for research on instructional strategies that would allow for the development of student self-regulatory skills. implications for future research and practice, as well as the position of online learning within the broader aspect of digital learning are further discussed.