WordPress is supposed to be used on a web server, which is running the programming environment PHP.
If you want your site to be reachable from any computer, then the best option is to use some web hosting provider company. You’d also need a domain name for this.
In order to install WordPress on the hosting provider’s file system, you’d need to connect to their file system, most probably using the internet protocol FTP, for instance using the free program FileZilla. However, virtually all hosting providers provide you a convenient one-click installation, too.
If you want to play with WordPress on your own computer, then you’d need a set of programs that will provide the necessary environment for WordPress to run, namely a database engine, and a web server with PHP.
You’ll find them if you google for MAMP, WAMP, local by flywheel, etc.
If you get stuck, search for “install WordPress localhost Mac”, and you’ll find loads of help.
Oh. One more thing: To your computer/editor, a PHP file is just a text file, where the file name ends in .php.
You can edit PHP files with normal text editors, but en editor that highlights the PHP syntax will help you to spot errors in your code more easily.
