The Authorization Code is an OAuth 2.0 grant that regular web apps use in order to access an API.
More on this flow: https://www.developer.saxo/openapi/learn/oauth-authorization-code-grant
Interactive demo: https://saxobank.github.io/openapi-samples-js/authentication/oauth2-code-flow/
A good tutorial on this grant type: https://auth0.com/docs/api-auth/tutorials/authorization-code-grant