An Xtream-style login generally asks for a server address, username and password rather than a single playlist file. Compatible software uses that account information to request available categories and streams from the corresponding service interface. The exact fields and supported features depend on the app and server implementation being used.
A practical example
A television app can show separate fields for the server, username and password. Pasting a complete M3U URL into the server field may fail because the app expects the base server address and the account details in their own fields.
A common misunderstanding
The words Xtream or XC do not establish a particular provider, official app relationship or catalogue. Follow the format issued for the actual account rather than deriving credentials from examples.
Related terms
Stable technical definition. Editorial approach