What is a Terminal (or "Terminal Emulator")? How do I run text based commands on my computer?
The terminal is left over from a time when all a computer could show was text. (And at the time, most computers were as big as a large refrigerator, so your personal screen and keyboard were only a low-powered "terminal" connected to such a "mainframe computer", at least until the "Personal Computer" was made.)
Back in these days, a computer user would interact with their computers with a keyboard only, typing in specific commands and getting the results.
It turns out typing commands like this is still really useful today, so this technology and way of interacting with the computer lives on. Using the terminal is still common for programmers, who need to run "low-level" or basic programs, which can be (arguably) more efficient on the command-line interface than with graphical interfaces.
Open the Start menu, and type either "cmd" for a very basic terminal, type "Powershell" for a similar terminal that's a bit more advanced, or type "bash" for an even more-advanced terminal. (You probably have "Git Bash" installed if you have installed Git, otherwise you probably do not have bash on your Windows computer. Downloading Git for Windows is a good way to get bash on Windows.) Bash is a more Unix-style experience, even though Windows is not very similar to Unix "under the hood" and many things will work differently in Windows than in macOS or Linux.
Open your App Launcher from the dock, or Spotlight (Cmd + Space) and type "Terminal". your terminal program is a powerful Unix-style shell running Bash (or Zsh, for new user accounts on macOS 10.15 Catalina and newer).
Open your application menu or application launcher, and type or click on any program with "Console" "Terminal" or "Terminal Emulator" in the name. This will usually run a Bash shell, and just like on macOS, this will usually be a powerful, Unix-style shell.
On macOS or Linux (or Bash on Windows), type ls and hit Enter. This will show you a list of files located at whatever folder your Terminal program is running in.
in CMD or Powershell on Windows, type dir to list the files in your current folder.
Now in any terminal or command line program, type cd .. and hit Enter again. This moves your terminal session up to one folder above the previous folder.
Terminal programs will always run in a specific folder no matter what. Sometimes this is important to how a "command" runs, since every command is understood to be run in the current folder unless you specify otherwise.
Here are three fine guides for beginning to use the Terminal:
And these are some more guides for each operating system: