What are you trying to do with the Terminal?
If you don't understand how to use the Terminal command line, then you should learn about it before doing anything else. The command line is extremely powerful and dangerous which can destroy macOS and all your data if used incorrectly or if you mistype a command (even for experienced command line users). The macOS GUI interface tries to protect users from making big mistakes, but the Terminal app has no protections for the user. When you execute a command from the Terminal app it will do exactly as told (even if the result wasn't what you intended). Make sure to have a good backup before doing anything with the Terminal command line.
Here is a basic introduction to the command line:
https://www.taniarascia.com/how-to-use-the-command-line-for-apple-macos-and-linux/
Again, this is very important: Make sure to have a good backup before doing anything with the Terminal command line.
Edit: Do not blindly use commands you find online. Many times the commands need to be customized for your own use. Make sure to understand the command(s) before executing them.