Okay, let's pretend you're out in the woods and you see a really cute animal with big antlers. You might think it's a deer, because that's what it usually looks like.
But let's say someone else comes along and calls that same animal a horse. That might sound silly, because horses are usually taller and have a different shape. It would be like calling your pet kitten a dog - they're both animals, but they have different names because they look and act differently.
When we use different names for different things, it helps us understand and communicate better. So it's important to learn the right names for things, even if they might look similar to something else.