Is the universe finite or infinite? This question has puzzled scientists for many years. Starting from general relativity and the Big Bang model, we can explore three possibilities: a universe with positive curvature, zero curvature, and negative curvature. Positive curvature suggests a finite but unbounded universe, while zero and negative curvature imply an infinite and unbounded universe. Observing the density of matter in the universe and the deceleration factor can help us determine the true nature of the universe. Current observational results indicate that our universe may be infinite and unbounded, but it could also be finite, unbounded, and oscillating. Despite this, we still cannot ascertain the exact state of the universe.