The "Authzcode," more commonly known as the "OAuth Authorization Code" is used in the Authorization Grant process. This specific OAuth process is used, when an application needs to ensure that a resource owner's credentials are never shared with the client. This specific use case can come into play when the client is running untrusted code, such as an app that needs privileged access. Below is a quote from RFC-6749:
The authorization code provides a few important security benefits, such as the ability to authenticate the client, as well as the transmission of the access token directly to the client without passing it through the resource owner's user-agent and potentially exposing it to others, including the resource owner.