Main Sequence Stars are a category of stars that are in a stable phase of their life cycle, where they fuse hydrogen into helium in their cores. This process generates energy, allowing them to shine brightly for billions of years. The Sun is a prime example of a Main Sequence Star, classified as a G-type star. These stars vary in size, temperature, and brightness, forming a continuous band on the Hertzsprung-Russell diagram. As they exhaust their hydrogen fuel, they will eventually evolve into red giants or supergiants, marking the next stages of their life cycle.