A username is a unique identifier that allows a user to access an online account or service. It is often combined with a password to ensure security. The username can be a person's name, an email address, or a custom name chosen by the user. A password is a secret word or phrase that protects the account from unauthorized access. It should be strong, combining letters, numbers, and symbols, to make it difficult for others to guess. Together, the username and password form a basic authentication method used by many online platforms, including social media and banking websites.