This lecture covers the Galilean relativity, studying relative motions in inertial coordinate systems within Newtonian mechanics. It explains the conditions for two inertial coordinate systems to have rectilinear and uniform relative motion, as well as the mathematical expressions for transformations between them. The lecture also discusses events defined by time and spatial coordinates, synchronized clocks, and the advantages of condensing spatial and temporal data into a four-dimensional vector for visualizing motion in space-time.