What an EPG is, and what XMLTV has to do with it
The EPG is your TV guide. XMLTV is the file format it arrives in, and it is a separate download from your channel list.
Short answer: the EPG is the program guide: what is on now, what is on next, and the schedule for the days ahead. XMLTV is the file format almost every service publishes it in.
Two separate things
Your channel list says which channels exist. The guide says what is playing on them. They are different files, often from different addresses, which is why you can have perfect channels and an empty guide.
How programs find their channel
By name. The guide says “this program is on Channel X”, and your player looks for a channel called that. If your list calls it something slightly different, that channel ends up with no guide. Tidying names with the Title Optimizer fixes more of these than anything else.
What a guide unlocks
- Now and next on every channel, and a full grid.
- Reminders before a show starts.
- Scheduled and repeat recordings, which need to know when a program is on.
- Catch-up, which is addressed by program.
The guide is the biggest download in any sync, so it finishes after your channels do. That is normal, not a fault.
Add one: Add an XMLTV guide address. Fix one: The guide is empty or wrong. Background: what an EPG actually is.