This chapter explores learning about the teaching profession that takes place in the practicum by applying the perspective of situated learning to study the role of other actors as a driver of learning, the modalities of appropriating contributions from the other by trainee teachers (TTs), and the professional knowledge they learn. It includes an exploratory case study with 13 TTs from two Chilean training centers. The self-confrontation interview was used as an information production technique, with a total of 28 hours of audio recordings that were transcribed and codified by means of analysis of conceptualizing categories. The results show that interaction with different actors is a source of production of learning. The presence/absence of educational intentionality in the involvement of the other with regard to the professional learning process of the TTs also leads us to consider interactions that are pedagogized, that is to say, the elements that emerge are intended to be understood as professional knowledge, while others lack an educational objective. Finally, the different modalities of knowledge appropriation share the fact that they represent different ways of exploiting the other as a driver of learning and building professional knowledge that is contextualized in the pedagogical interventions of TTs