You open one web address and the browser finishes at another. That may be a redirect rather than a typing mistake. MDN’s HTTP redirection guide describes how redirects direct requests to a different location, including permanent and temporary forms.
Record both addresses
When reporting unexpected behaviour, save the address you started with and the final address shown in the browser. Note whether the change happens every time and whether you followed a link or typed the address yourself.
Do not infer the redirect type solely from the fact that the address changed. The technical response and implementation need inspection if the distinction matters. A visible change tells you the outcome, not the complete mechanism.
Check the destination before continuing
If an unexpected page asks for credentials or payment information, verify that you have reached the intended service through a trusted route. A redirect can be legitimate, but it does not itself establish that the destination is trustworthy.
For an ordinary support report, the two addresses and a short description are often the most useful starting point. They let the site owner investigate the path you actually followed instead of guessing from a screenshot of the final page alone.