Dinosaur classification is the process of organizing dinosaurs into groups based on their physical characteristics and evolutionary relationships. Dinosaurs are primarily divided into two main categories: Saurischia, which includes theropods like Tyrannosaurus rex and sauropodomorphs like Brachiosaurus, and Ornithischia, which includes dinosaurs like Stegosaurus and Triceratops. These categories are further divided into subgroups, allowing scientists to study the diverse range of dinosaur species. By examining fossils and anatomical features, paleontologists can better understand how these ancient creatures lived and evolved over millions of years.