What is something that exists only because humans collectively agreed to believe in it?

Can I still earn money while living abroad on a retirement visa, and what kind of online or virtual jobs would be suitable for someone my age?
Why do INFPs find it hard to be pragmatic and street-smart, and what strategies can they use to become more practical without losing their idealism?
Why do we sometimes act silly while we're still aware of our actions? It's like the third-person narrative in literature.