HTTP Redirects are used to forward a domain visitor to another domain. Once the destination is reached, the domain name also changes in the browser address bar.
A visitor goes to ionos.co.uk, which is then redirected to help.ionos.co.uk. The visitor sees the contents of help.ionos.co.uk, and the address entered into the browser (ionos.co.uk) changes to the destination (help.ionos.co.uk).
This redirection is recommended as standard instead of using a Frame Redirect.