terminal
I'm using Terminal.app version 2.9.1 which is built into macOS. I just learned that I can split the screen vertically using Command + D (and un-split it via Command + Shift + D).
However, I do not understand how to use the two views differently. In fact whenever I type a command in the lower screen, say ls, the same happens in the upper screen.
Also, I do not understand how to use the upper screen. I read somewhere that Command + Alt + ↑ should do the job, but that doesn't seem to work.
It's meant to be like that. See this Super User answer:
You're misinterpreting the feature. It's not meant for two separate terminals. It's intended to allow a user to see two different view points in the same terminal. For instance, if you have 3000 files in a directory, and you perform an ls command, that output is going to be very long.
If you use the split pane, you can scroll through that long output without having to flip back and forth, possibly losing your place along the way.
If you want two terminals, use tabs, or separate windows.
I would add that, for two separate terminals, you can use separate tabs as well.
Edit: Disregard the first part. [ Is the shift of { so we were saying the same thing different ways. I'm leaving this here though regarding disabling the Mission Control shortcuts.
The sequence to cycle forward through tabs is ⌘+shift+}, despite what the Window menu says. (⌘+} switches between windows. Very odd.) And ⌘+shift+{ cycles backward.
(You should also be able to reclaim ⌘+1, ⌘+2, etc. to switch windows in Terminal, which is what the Window menu says those shortcuts do, by going to System Preferences > Keyboard and disabling the keyboard shortcuts that use cmd+ a number under Mission Control. I haven't tested this though.)
Best Answer
From this answer:
Alternatively, you can also install and use a widely used 3rd party Terminal emulator called iTerm2. iTerm2 has various features including the ability to create Split Panes, with support for keyboard shortcuts.