Webhooks are user-defined HTTP callbacks that trigger an HTTPS POST request to a specified URL whenever a particular event occurs, such as pushing code to a repository or posting a comment on a blog. They automate tasks by enabling real-time updates and data synchronization, offering advantages over traditional polling methods. Implementing webhooks effectively requires adherence to best practices, such as securing endpoints, authenticating requests, and using protocols like Network Time Protocol (NTP) to prevent replay attacks. Webhooks find applications across various domains, including e-commerce, communication platforms, and email marketing, with platforms like Shopify, Discord, and Mailchimp utilizing them to enhance functionality and efficiency. Developers can integrate webhooks into their authentication and development strategies by setting up secure endpoints and using methods like secret keys to verify request authenticity, ensuring that only trusted sources can trigger actions within their systems.