Student learning at the university level occurs in a variety of settings, both formal and informal. Prior research shows that retention of knowledge is enhanced when students teach material related to their learning. In this study, we explored student perceptions of learning experienced through facilitation of informal physics programs, also called outreach, where they frequently practice methods of self-explanation to diverse audiences. To characterize the impacts of these facilitation experiences, we employed a student-centered investigation drawing on self-reported data gathered through didactic interviews conducted with 35 students who facilitated at least one of five informal physics programs. Analysis of interviews drew on multiple learning theories to characterize perceptions of understanding of physics concepts, confidence in their knowledge, and how those constructs related to engagement with members of the public through outreach. Using network analysis, we found three distinct clusters of themes focusing on disciplinary learning, internal development, and external engagement.