Stellar refers to anything related to stars, which are massive celestial bodies composed mostly of hydrogen and helium. They generate light and heat through nuclear fusion in their cores, creating energy that radiates into space. Stars vary in size, temperature, and brightness, and they are classified into different types based on these characteristics. The study of stars is a key part of astronomy, the science that explores the universe beyond Earth. Stars are often grouped into constellations, which are patterns formed by their positions in the night sky. Understanding stellar properties helps scientists learn about the life cycles of stars and the formation of galaxies.