When user browsing a website, the website’s contents will cache in your browser. This cache can be controlled by using to configure Cache-Control HTTP headers for your website, This is done by adding mod_expires in the .htaccess file of your server.
If you don’t use Cache-Control HTTP headers, then, you will have a longer wait times when browsing your website. Each time your website is accessed without Cache-Control, your website has to make a request to the server for each content as image, html file, jquery file, javascript file, CSS file, and so forth to load.
HTACCESS mod_expires Module instructs Apache to generate Expires and Cache-Control HTTP response headers for the specified content types. Web browsers parse these HTTP response headers to determine how long to cache content on the client’s machine browser.