When smart phones first hit the scene and were becoming increasing popular for web browsing, many businesses realised that they needed to ensure that their website would work correctly on these sorts of devices. Often the simplest solution was to create a standalone version of the site which would only be showed to mobile users. This allows you to change menus, display different content and remove elements that may not be mobile compatible without affecting the main site.
The issue with many of these sites is that the mobile version often seemed to be very stripped back and looked quite plain and you may have to remove functionality that is actually a good selling point,
Ideally you want to have a mobile version of your site that looks likes your desktop version (using same colour ways, logos etc,) but is easier to use. This may mean changing the navigation to buttons along the side rather than having to zoom in and out to navigate different parts of the site.
It is quite easy now to adapt your main desktop website to be mobile compatible by setting view points and making sure your elements are responsive.