TBH, in all my years of Linux usage, I've never used any of them! :/
What are they used for? From what I can see they appear to be used for controlling multiple terminal sessions... Is that correct?
I tend to use dwm as my main desktop environment nowadays (tiling window manager). So if I start multiple terminal sessions, each terminal session appears in a different pane on the screen (in tiled mode) and I can use simple key-binds to switch between sessions. If I want to view the current session in full-screen I can switch to monocle mode with another key combo.
I also switched to using Terminator as my terminal of choice a few years ago, so I can also create additional terminal sessions in horizontal or vertical splits in the main terminator window. Again, navigation between the sessions is done with simple key-binds.