Theropods - Bipedal dinosaurs that were mostly carnivorous, birds are descended from this group! Some Theropod examples are Velociraptor and Tyrannosaurus Rex

Sauropodomorphs - Sauropodomorphs were dinos with long necks and small head, there are two subclasses for them
1. Prosauropods - Prosauropods were much smaller than the giant sauros. Some examples are Plateosaurus and Massospondylus
2. Sauropod - Sauropods were the giant long-necked herbivores, all sauropods were quadrupeds, unlike the prosauropods. Some examples are Apatosaurus (formerly Brontosaurus), Camarasaurus, Brachiosaurus.

Heterodontosaurs - Heterodontosaurs were small, bipedal herbivores with tusks and flexible tails, some examples are Tianyulong and heterodontosaurus

Thyreophorans - Basically dinosaurs with plates/bony studs on their back. Some examples are stegosaurus and ankylosaurus