This lecture delves into the concept of linear independence of vectors, focusing on linear combinations efficiently represented by matrix products. It explores matrices as functions transforming vectors, discussing properties and geometric implications. Linear applications, synonymous with functions or transformations, are thoroughly examined, showcasing practical examples. The lecture demonstrates how matrices create transformations and applications, emphasizing the importance of understanding linear transformations in various dimensions. Through concrete examples, the lecture illustrates how matrices transform vectors, emphasizing the geometric interpretations and the concept of projections. The discussion extends to the uniqueness and properties of linear transformations, culminating in a deeper understanding of matrices and their role in linear algebra.