When you browse Wikipedia on your mobile phone the domain of Wikipedia usually is "https://en.m.wikipedia.org" instead of "https://en.wikipedia.org" on a desktop computer. Most mobile browsers such as Firefox for Android have an option called "Request Desktop site" which shows you the desktop version of the same website. But when you try to request the desktop site in Firefox for Android, the actual desktop site is not shown but only the mobile website with a different layout.
You browse https://en.m.wikipedia.org/wiki/Apple on your mobile phone. Then you click "Request Desktop site" in your mobile browser. You would expect to be redirected to https://en.wikipedia.org/wiki/Apple (without the ".m.") but instead you are still on the mobile page but just with a different layout (wider screen, etc.).
When you browse the mobile website of Wikipedia and click "Request desktop site" in your mobile browser you should be redirected to the desktop Wikipedia site without an ".m." in the domain.