M3U is a playlist format that lists media locations and can include descriptive information understood by compatible players. The entries may reference files, internet resources or streams. A playlist organizes access points; it does not contain a whole television catalogue inside itself or establish that every listed resource is reachable and authorized.
A practical example
A simple M3U file can contain two media addresses that a player opens when their entries are selected. If one address changes or becomes unavailable, the other can still work because the entries refer to separate resources and requests.
A common misunderstanding
A channel name in a playlist is a label, not proof of its content, language or current availability. Treat private playlist addresses as account information when they include credentials.
Related terms
Stable technical definition. Editorial approach