This lecture covers the concepts of Einsteinian relativity and the Poincaré Group, focusing on changes of coordinates preserving the group structure. It delves into the Lorentz group, Lorentz Lie Algebra, and Lorentz boosts, emphasizing the importance of proper and non-orthochronous components. The lecture also discusses the Lorentz Lie Algebra simplification and the commutation relations within the group. Furthermore, it explores the finite group formations and the complexification of Lie Algebras, providing insights into Lie parameters and representations.