If we imagine the world and what surrounds us as concepts, if you then had to explain these ideas (i.e. What's a person? What's an animal? What's a living being? ...) you'd then need to recursively explain other concepts. What would be the simplest idea(s)?

Let's pick a person as an example. You could say a person is a thinking animal, you'd then need to explain what thinking and thought means, and what an animal is. From that you'd need to explain what their 'parent' ideas are etc.

What concepts can instead be explained without explaining other concepts?