The ID Token is a JSON Web Token (JWT) that contains user profile information (including items such as the user's name and email) which is represented in the form of claims. These claims are statements about the user, which can be trusted if the consumer of the token can verify its signature.
You can get an ID Token for a user after they successfully authenticate.
Additionally, you can learn about your options for renewing a token. Which option to use depends on the type of application you have, and is covered in more detail in the Refresh Tokens document.