Responsive websites display correctly not only on personal computers but on mobile phones also. Some elements of the website change their width/height depends on the device’s display resolution. Such websites have much better ranking on Google and these days people mostly use mobile phones to surf the web so any website needs to be responsive actually. For example, if you create a contact form with aidaform but it’s too wide, someone who’ve visited your website from a smartphone won’t fill this form because it’s not convenient enough.