One of the most difficult things to get started with Web Development is installing all the programs in your environment. We're going to run a series of commands to provision the environment.
During the process, you shouldn't worry too much about "why" you're doing what you're doing. Just know that these steps are the steps it takes to provision a web development environment using vagrant (which many students continue to use even after graduation).
Sometimes you will be prompted for a password (your computer login password, user account, etc.) when you're installing programs using the terminal window. When you start typing the password, it will look like it nothing has been typed (eg. nothing will display on the screen as type). That's totally fine. Your password is being entered, just not shown to you. So keep typing and press enter when you're done typing. In case you type your password wrong it will prompt you to type in your password again. Why? So nobody can look over your shoulder and see your password or know how many characters your password has.