HTTP Security Headers are special instructions sent by a web server to a user's browser, enhancing the security of web applications. These headers help protect against various online threats, such as cross-site scripting (XSS) and clickjacking, by controlling how content is handled and displayed. Common types of HTTP Security Headers include Content-Security-Policy, which restricts resources the browser can load, and X-Frame-Options, which prevents the site from being embedded in iframes. Implementing these headers is crucial for safeguarding user data and maintaining the integrity of web applications.