This lecture covers the concepts of vector subspaces and linear combinations in linear algebra. The instructor emphasizes the importance of understanding how to determine if a set is a vector subspace and how to find linear combinations. Topics include rectorial sub-spaces, equivalent subspaces, and the properties of vector spaces. The lecture also delves into the relationship between lines, columns, and elements in a vector space, highlighting the reciprocal nature of these elements. Through examples and exercises, students learn to identify vector subspaces and determine the validity of statements based on linear algebra principles.