Adult learners make up a significant portion of college and university students in the United States, but awareness and data around this population and their challenges, particularly for students enrolled in online programs, are lacking. Practitioners and others in the ecosystem also lack research into the experiences of adult students disaggregated by gender, race, and ethnicity. Given the ways in which student challenges and opportunities for postsecondary persistence, engagement, and completion differ for these groups, gaps in understanding limit the ability of postsecondary institutions and policy-makers to better support adult learners on their journeys to post-secondary degrees and credentials that position them for economic success. To address these gaps, JFF investigated the available literature and evidence on adult learners, including their collective characteristics, experiences, and outcomes. This report reviews of adult learners in the context of the U.S. postsecondary system, with a particular interest in online settings and Black learners. The report examines data around enrollment, persistence and demographics, before reviewing scientific evidence regarding adult learner practices.