Show practical judgement: "For a marketing site where the client needs full layout control, I use a block theme with theme.json design tokens. For a complex application site with dynamic logic, a classic theme with targeted block support gives more control."
Classic themes use PHP template files (header.php, single.php, archive.php) with the template hierarchy. Block themes use HTML template files with block markup and theme.json for global styles and settings. Block themes enable Full Site Editing — users can modify headers, footers, and templates visually. Choose classic themes for complex dynamic logic or when clients need minimal editor access. Choose block themes for content-heavy sites where editorial flexibility matters. Strong candidates discuss: theme.json for design tokens, template parts for reusable sections, the template hierarchy in both systems, and hybrid approaches using block template parts within classic themes.
Tests awareness of modern WordPress direction. Candidates who only know classic themes are not keeping up. Those who understand both approaches and can articulate when each fits show mature WordPress expertise.