Information and communication technologies have invaded the field of training, though their performances have been judged by companies to be insufficient. Among the origins of this state of affairs, the author considers that the lack of knowledge of what happens in a "real use situation" plays an important role. Indeed, understanding what is involved in learners-system interactions is fundamental to improve the system appropriation and its efficient usage. This appropriation is a dual necessity for learners as they must take over the offered possibilities of interactions and acquire the necessary knowledge. As appropriation is made through offered interactions, the author considers computer interactions traces as potential appropriation facilitators. This conceptual article presents bibliographical research concerning the use of computer interactions traces and proposes a classification of 'tracing systems'. Additionally, the links between these works and the process of appropriation in an instrumented training situation is provided, while the author also presents an experimental study conducted on the role of traces of interactions in a collaborative mediated task by using a numerical environment.