The dragon is a legendary creature belonging to the world of mythology, story telling and fantasy. There are stories about dragons in Chinese culture, European culture, South American culture, and many others.
Dragons can look like dinosaurs and other extinct animals. Because of that, it is easy to think that those animals might have been an example for dragons as they were thought of in the history of humankind.
There are many kinds of dragons in the different cultures. In general:
A dragon has: none to four legs, claws, scales and possibly spikes.
A dragon can look like a snake with wings, or like lizards.
A dragon has a tail and a long neck.
A dragon has a wide mouth with big and dangerous teeth.
Sometimes they have horns and hair.
A dragon can fly.
A dragon can perhaps breathe fire (or other dangerous substances).
A dragon has special powers.
Some dragons live in caves.
In stories such as The Hobbit or Beowulf, dragons are dangerous and attack humans. Other stories, such as those by Anne McCaffrey, have dragons who are looking for help, or giving help. A dragon also appears in the Book of Revelation chapters 12-13, where he is seen as the Devil.