 A model of general relativity, a  spacetime,  is a pair \((M,g)\). It represents a possible universe compatible with the theory. Here, \(M\) is a manifold of events. It gives the shape of the universe. (Lots of two-dimensional manifolds are familiar to us: the plane, the sphere, the torus, etc.) Each point on \(M\) represents a localized event in space and time. A supernova explosion (properly idealized) is an event. A first kiss (properly idealized) is also an event. So is the moon landing. But July 20, 1969 is not an event. And the moon is not an event. 