What are HTTP response headers?
Response headers are sent back to the web browser. When a page or file is requested by a web browser, the file content is sent back to the web browser. Simultaneously, the HTTP headers are attached with the file content. The HTTP headers provide information about the contents of the file, such as the file size and the code that the file has been created.
The HTTP headers also tell other technical information about the server, normally the software manufacturer of the web server, or whether the file content is compressed and if the contents of the file can be cached.