This lecture introduces the fundamental concepts of structural mechanics, focusing on static (rigid) structures and mechanisms. Topics covered include statical determinacy, different types of joints/supports, equilibrium in 2D and 3D, and the analysis of truss structures. The lecture also discusses the concepts of statical determinacy, kinematic determinacy, and hyperstatic systems, emphasizing the importance of understanding the equilibrium of structures. The presentation progresses from the theoretical representation of a body to the practical application of static and kinematic determinacy in structural analysis.