What is a WordPress block theme (block-based theme) and how does its `theme.json` differ from classic theme approaches?

Question

WordPress Fundamental — Hard

What is a WordPress block theme (block-based theme) and how does its `theme.json` differ from classic theme approaches?

Accepted Answer

A block theme uses block templates and template parts instead of PHP files; theme.json provides a centralized configuration file for styles, colors, and typography. This streamlines design settings that previously required multiple PHP, CSS, and JavaScript files.