A dinosaur is a type of animal that lived on Earth millions of years ago, long before humans existed. Dinosaurs first appeared about 230 million years ago during a time called the Mesozoic Era, and they ruled the planet for over 160 million years. Some dinosaurs were huge and terrifying meat-eaters, while others were gentle plant-eaters that traveled in groups.

What makes dinosaurs special is that they walked with their legs directly under their bodies, not spread out like lizards. This helped them move faster and grow much larger than most other animals of their time. Dinosaurs lived on land, laid eggs, and came in many shapes and sizes—from small, chicken-sized hunters to giants taller than buildings.

Even though most dinosaurs went extinct about 66 million years ago, they didn’t completely disappear. Scientists have discovered that modern birds are actually living dinosaurs, meaning dinosaurs still exist today—just with feathers and wings.