If you've built static sites before, you'll know that they consist of a number of files that you upload to your server. These will include:
HTML files
One or more CSS files (referred to as style sheets)
Possibly JavaScript files if you're running sliders or other dynamic elements on your site
Your WordPress site will include different file types and it will also include a database, which is where your content will be stored.
The main elements of a WordPress site are:
The files running WordPress itself. These are mainly PHP files.
The files in your site's theme, including one CSS file (occasionally more) and a number of PHP files.
The files in any plugins you install. These will always include PHP files but may also include CSS and JavaScript files.
Files you upload to your site, including images and PDF files.
Your site's database, which will include a number of tables storing your content and site settings.
You'll learn more about these and what they do in the next section.