How can I best get a good understanding of how it all works? So there are many different platforms but they all take from a small number of content providers yes?

Yes.

Then they have different methods of getting this to you... Generally though a username and password, or an m3u link which contains your username and password. You can load this into a large number of different apps - and each of those apps has a different style of UI, is that correct? What are the most popular apps etc? Are there other ways also, what are the main ones?

Smarters, TiviMate, IMPlayer, XCIPTV, PerfectPlayer, GSE.

So many IPTV services seem to vary so wildly I don't understand. Some are clunky as hell and some look really slick. Some just have lists of movies randomly others have netflix style options. How do I find a good one?

Generally, if you’re supplied a m3u link, you want m3u_plus which has categories of channels. The ‘Netflix’ style parts are called VOD (video on demand).

I started this journey looking for the 24/7 tv series looping channels which I love. Are they all the same or do some have better quality etc? Some are very old but some should be hd but are not, I don't get it. I just want that and a reasonably decent delection of movies and tv series - but with a really nice interface. Its hard to know where to start!

I think 24/7 is different for most providers. Some have more than others, some better quality than others.

For a decent VOD with a nice interface, I’d suggest you look into Plex or Emby shares. /r/plexshares or /r/embyshares have suppliers and information.

One other question is technically how does this even all work? I'm kinda fascinated as to where it all comes from and how come a teenager in his bedroom seems to be able to set up his own iptv service?

Top suppliers subscribe to TV services and use software to send the stream out. Providers buy groups of streams from these suppliers. The ‘teen in his bedroom’ is most likely a reseller of a service. There’s a management panel where they can buy credits at a discount and then sell access using said credits.

247 are completely hit or miss. If you're trying out services I suggest paying attention to the syntax in regards to channel naming. Many many services just restream the same 247 channels. So jumping to another service may not actually get u new channels. If you find any unique channels it may be an indicator that this service can actually make their own channels.

Nitro has the most unique ones, they would make new ones out of sporting events or anime etc. Venom/absolute/tpk all share the same 247 but they have some unique ones you won't find elsewhere ( British tv, panel shows )

Jager vision had a good categorized selection before The Event

247 channels can be set up by creating a VLC playlist out of whatever you want, and streaming it via http.

I would STRONGLY suggest finding a service that has most of the channels you want and then make your own. Check my posts. If you can't figure it out I can guide you through. I have 12 or so running on my computer that I made into my own M3u.

Making your own 247 channel results in getting a URL that points to your video stream, much like a regular internet video. That URL gets put into an M3U which is just a playlist of various channels and their respective video links.

This might not be your platform of choice but the Emby wiki does a good job of explaining. I assume this is the same across the board.

https://github.com/MediaBrowser/Wiki/wiki/Live-TV

I'm just starting out. I know now I need to do the following.

Add a Tuner (M3U files). I believe you can make your own M3U files if you want. Add Guide data if required. Channel Mapping.

I'll try out free ones for now, maybe pay for some, or start building my own. I could start with BBC1, BBC2 etc.. Then I want to learn recording them.

Have you tried Google for your questions????...its all kinda complex for some guy to type out on here