Tokens are basically random strings, much like a password, and can provide a simple authentication mechanism in some situations. However, tokens are only as safe as they are secret so other authentication schemes can provide more security in large installations.
For this example, start the server using:
> nats-server --auth mytoken
The code uses localhost:4222 so that you can start the server on your machine to try them out.
Some client libraries will allow you to pass the token as part of the server URL using the form:
Again, once you construct this URL you can connect as if this was a normal URL.