Authentication is the process of verifying that an individual, entity or website is whom it claims to be. Authentication in the context of web applications is commonly performed by submitting a username or ID and one or more items of private information that only a given user should know.
Authorization may be defined as “the process of verifying that a requested action or service is approved for a specific entity” (NIST). Authorization is distinct from authentication which is the process of verifying an entity’s identity. When designing and developing a software solution, it is important to keep these distinctions in mind. A user who has been authenticated (perhaps by providing a username and password) is often not authorized to access every resource and perform every action that is technically possible through a system.
For example, a web app may have both regular users and admins, with the admins being able to perform actions the average user is not privileged to do so, even though they have been authenticated. Additionally, authentication is not always required for accessing resources; an unauthenticated user may be authorized to access certain public resources, such as an image or login page, or even an entire web app.
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