How do infants extract useful information from a world of distractions? Social learning from others enables infants to acquire information rapidly and efficiently that otherwise would require more time and cognitive resources. In this paper, we aimed to clarify the social learning mechanism of infants by focusing on from whom and how they learn. First, we introduced the theory of natural pedagogy, which argues that young infants can acquire knowledge from ostensive signals. Second, we reviewed recent studies on infant social learning from the viewpoint of two critical factors: agents and ostensive signals. In particular, we provided studies that focused on what type of agent is appropriate as an information source for infant learning and how ostensive signals work effectively for infant learning. Third, we provided tentative suggestions on how the foundations of infant social learning are generated, maintained, and formed in early development.