Use the terminal app to access command line tools.
Mac OS uses the ZSH as the default shell. Oh my ZSH! is a nice package that gives you some great add-ons.
A package manager is software that helps you manage applications installed using the command line. It helps keep tools up to date and allows you to have multiple versions of software installed.
Mac doesn’t ship with a package manager but homebrew is by far the most popular and is really useful. You suggest install it!