At the very minimum, a WordPress Theme consists of at least two files, plus an optional 1200×900 image to suggest the theme’s design :
A child theme can be even simpler because it inherits the functionality and styling of
a parent theme. It can be done with one file that imports the parent style.css.
But the current best practice is to use a functions.php that enqueues the parent style.css file:
Child themes are the best way to make major modifications to an existing theme. *
- ensure modifications are preserved
- speed up development time
- learn about WordPress theme development
* minor modifications to style can be done using the theme’s Customize feature.