Identity tokens are used to convey information about a user's identity, including their unique ID, email, and name, and are typically returned to the client application after successful login. Access tokens, on the other hand, are primarily used for authorization purposes, such as accessing protected resources, and contain claims like permissions or scopes that define what the user can do. Properly separating identity tokens and access tokens is crucial for building secure authentication and authorization flows, and mixing them up can expose security holes. Best practices include using identity tokens to personalize applications and display user information, and using access tokens to call APIs while scoping their permissions carefully.