what's the difference between a reindeer and a deer

Reindeer, or caribou as they are also known, are a species of deer that live in the Arctic and subarctic regions of the Northern Hemisphere. They are the largest species of deer and can weigh up to 500 pounds. Reindeer are distinguished from other deer by their thick coats, large antlers, and their ability to survive in harsh environments. Reindeer are also unique in their ability to pull heavy sleighs and fly through the air like Santa's magical flying reindeer.