In this talk, I extend the enactive approach to cognition to the social domain within a larger framework of varieties of intentionality and argue for a second-person approach to understanding others, emphasizing a difference in our understanding of others depending on whether we are directly engaged with them in interaction or merely observing them. The enactive account is especially persuasive in developmental respects, suggesting that sophisticated forms of cognitive intentionality (e.g. believing) are grounded in motor intentionality (e.g. perception and action): Our own sensorimotor skills are partly constitutive of cognition, and other peoples expressions of their sensorimotor skills in turn modulate our cognition of objects and our social understanding. The enactive account explains how young infants acquire the capacities that allow them to move from dyadic to triadic intentional relations at around their first birthday, and it claims that our basic form of social understanding is neither based on theoretical inference nor a kind of simulation, but constituted by an embodied implicit know-how displayed in online interaction.