Final answer:
The Sun is a star, characterized by its enormous size, hot incandescent gas surface, and ability to produce light and heat through nuclear fusion at its core.
Step-by-step explanation:
The Sun is classified as a star. This massive object at the center of our solar system is a gigantic ball with a diameter of about 1.4 million kilometers, featuring surface layers of incandescent gas. Inside, it boasts an interior temperature reaching several million degrees. Stars, including our Sun, generate great amounts of energy through nuclear reactions deep within their cores. Stars are distinct from brown dwarfs, which are a class of objects with masses between stars and planets and are not capable of sustaining hydrogen fusion, and from planets, which are defined by their orbit around a star and lack of self-sustained light emission. Through its nuclear reactions, specifically the fusion of hydrogen into helium, the Sun radiates light and heat that support life on Earth.