Red giants are large, evolved stars that have exhausted the hydrogen fuel in their core and have started burning helium instead. They are typically much larger and brighter than main sequence stars like the Sun, and have a reddish hue due to their lower surface temperatures. Red giants are found in the later stages of stellar evolution and are among the most common types of stars in the universe. They play an important role in the life cycle of stars, as they eventually shed their outer layers to form planetary nebulae or undergo supernova explosions. Research on red giants focuses on their properties, evolution, and impact on the surrounding interstellar environment.