Authentication is the process in which we are checking the identity of the user to allow the user into the application. So Login is the process of authentication for the application. Now social media authentication is also allowed in many websites to identify the user.

Authorization sounds same as authentication but it is different. Authorization handles the permission stuff for the user at web page level. Better example will be if the user is authenticated in the website does not mean that user has full permission on all the pages so that can be controlled by authorization.