What the M3U export gives you
The playlist file this site generates, what is inside it, and when a plain M3U beats a proper Xtream connection.
What the file contains
The M3U download builds a playlist pointing at the endpoint's full channel list, with your credentials embedded in the query string and an url-tvg attribute pointing at the same server's XMLTV guide. It is a two-line file: a header carrying the guide URL, and one entry resolving to the playlist.
Because the credentials are in the URL, the file is as sensitive as the password itself. Anyone you send it to has full access to the account.
When to use it
Use the M3U when the player you want does not speak the Xtream API — VLC, some smart TV apps, older hardware. Use a native Xtream connection everywhere else. The Xtream API gives you categories, series, video on demand and catch-up as separate structures; an M3U flattens all of it into one long list.
Opening it in VLC
VLC will play an M3U directly, but treat it as a diagnostic rather than a viewing setup. Media, then Open File, then pick the playlist; the channel list appears in the playlist pane. If channels play in VLC but not in your usual app, the endpoint is fine and the problem is app-side configuration.
Why the guide is often empty
The url-tvg attribute points at the server's XMLTV endpoint, but many panels either do not populate it or rate-limit it heavily. An empty guide is normal and says nothing about whether the streams work.