Previous work has identified that recognition from others is an important predictor of students' participation, persistence, and career intentions in physics. However, research has also found a gender bias in peer recognition in which student nominations of strong peers in their physics course disproportionately favor men over women. In this study, we draw on methods from social network analysis and find a consistent gender bias in which men disproportionately undernominate women as strong in their physics course in two offerings of both a lecture course (for science and engineering, but not physics, majors) and a distinct lab course (for science, engineering, and physics majors). We also find in one offering of the lecture course that women disproportionately undernominate men, contrary to what previous research would predict. We expand on prior work by also probing two data sources related to who and what gets recognized in peer recognition: students' interactions with their peers (who gets recognized) and students' written explanations of their nominations of strong peers (what gets recognized). Results suggest that the nature of the observed gender bias in peer recognition varies between the instructional contexts of lecture and lab. In the lecture course, the gender bias is related to who gets recognized: both men and women disproportionately overnominate their interaction ties to students of their same gender as strong in the course. In the lab course, the gender bias is also related to what gets recognized: men nominate men more than women because of skills related to interactions, such as being helpful. These findings illuminate the different ways in which students form perceptions of their peers and add nuance to our understanding of the nature of gender bias in peer recognition.