Any interviewer asking this question likely wants to hear that a WordPress theme is a collection of files that work together to create the design and functionality of a website. Themes typically contain a style.css file, which houses the main style rules and a functions.php file, which includes code to add features to the website. Themes also include template files, which control how different pieces of content are displayed on the site.

This is the sort of question that employers want to hear a detailed answer for. To create a custom post type, you need to use the register_post_type() function in the functions.php file of the theme to register the post type and then define its labels, arguments, and capabilities.