A geodesic is the shortest path between two points on a curved surface, generalizing the notion of a straight line in Euclidean space to non-Euclidean geometries. It is a critical concept in differential geometry and is used extensively in the theory of general relativity, where it describes the paths of particles and light in spacetime influenced by gravity.
Spacetime events are specific occurrences in the four-dimensional continuum of space and time, defined by a unique set of coordinates that specify a point in both space and time. They are fundamental to the theory of relativity, where the separation between events can be classified as timelike, spacelike, or lightlike, influencing the causal structure of the universe.