User Authentication is the process of verifying a user's identity before granting access to protected resources. It is an important security measure that helps to ensure only authorized individuals are able to access confidential information or accounts. Authentication typically involves presenting some form of credential, such as a username and password combination, biometric data, or even physical keys. The credentials are then compared against stored records that identify the user and determine whether they are allowed access. If authentication succeeds, users can be granted access to secure areas or operations; if it fails, they must be denied entry.