This is historical information about a function, "frame forwarding"/cloaked forwarding, which was removed several years ago.
See instead here for information about www forwarding and here for virtual hosts.
When users are forwarded using a WWW forwarding, normally the address they are forwarded to is shown in the address bar.
If you do not want this, you may check the checkbox for the original address to remain in the address bar, so-called "frame forward". Note: Please be aware that this feature may have many unwanted side effects:
- The target address that you are forwarding to does not allow such frame forwards, and will only display a blank page
- The content is incorrectly displayed on mobile devices
- Navigating on the page will not update the address bar
- Poor search engine visibility (SEO)
For the above reasons, we discourage the use of frame forwards. Instead, use regular WWW forwardings or DNS records.