A signed JWT is known as a JWS (JSON Web Signature). In fact a JWT does not exist itself — either it has to be a JWS or a JWE (JSON Web Encryption). Its like an abstract class — the JWS and JWE are the concrete implementations.
Following is a sample JWT, which is returned back from the Google OpenID Connect provider. Here the Google, which is the identity provider, asserts the identity of an end-user and passes the JWT to a service provider (a web or native mobile application).