CORS Preflight is a security feature in web browsers that helps manage cross-origin requests. When a web application tries to access resources from a different domain, the browser first sends an HTTP request called a "preflight" request. This request checks if the server allows the actual request by verifying the HTTP method and headers. If the server responds positively, the browser proceeds with the actual request. If not, the browser blocks the request to protect user data. This process ensures that only authorized domains can interact with the server, enhancing security in web applications.