Emacs Elements has an interesting video on something I didn’t really know about: 2-Column editing. I say “really know about” because I always assumed it was just another name for follow mode. But, of course, it’s an entirely different thing.
Even after watching the video and reading the Emacs manual entry, I still couldn’t give a clear explanation of its purpose. The TL;DR is that if you have a buffer that contains vaguely table like data where there’s some notion of columns, you can “split” the data between columns with each column being in its own buffer. These two buffers are displayed side by side and can be edited independently. When you’re finished editing, you can merge the two buffers back together.
I’m doubtlessly suffering from a lack of imagination but I’m having a hard time figuring out a use case for this. As far as I can see, you can do all the same editing almost as easily without learning the somewhat confusing 2-column commands.
You, of course, may disagree. Obviously some people do or the facility wouldn’t exist. Take a look at the video and see what you think. The video is 11 minutes, 42 seconds so it should be easy to fit in.