An M3U (or M3U8) file is a simple text file that holds the list of channels and streams for your IPTV service.
When you subscribe to IPTV, you often get an M3U link (URL). You paste this link into a player app like TiviMate, and it loads all your channels automatically. It is just the address list that tells your app where each channel lives. If your provider gives you a username, password and a portal URL instead, that is called Xtream Codes — a more convenient login that does the same job.
Galaxy plans come with a free trial so you can test everything before you buy — no jargon, we set it up with you on WhatsApp.