Every WordPress site uses a theme, which is a term that refers to a series of files that collectively determine how a WordPress site is displayed to visitors. WordPress themes are a collection of stylesheets (CSS) and templates, which together form your “theme.”
When you install WordPress, you’ll be prompted to choose from one of a few default themes, however, you can change your theme at any time. The official WordPress site has thousands of themes available, both free and paid, or you can download a theme from a third-party site.
To see which theme you are using, log into your WordPress administration area. In the left-hand column, click on “Appearance” and then “Themes.” Here, you can preview how the theme makes your site look or install a new one.
Note: Changing your theme does not alter any of the content you’ve produced. It only changes how it is displayed.
Some themes can be customized without any coding. If you see the option “Customize” under “Appearances” in the left-hand column of your administration area, this is where you can modify your theme with just a few clicks of the mouse.
Themes are, essentially, the guide for how every element of your WordPress website will be displayed to visitors. Everything from the overall layout to the fonts used and the different features available is determined by the theme.
Every theme has three different parts:
A stylesheet file (called “style.css”);
The template files (written in PHP); and
A “functions.php” file that allows themes to be customized by the website administrator without writing any code (this is optional and not used with all themes).
When choosing a theme, you can pick a generic style or one suited to a specific kind of website like a photography theme or a magazine style theme.