A topic cluster is an SEO content strategy where a comprehensive ‘pillar page’ covers a broad topic at a high level, while multiple linked ‘cluster pages’ explore specific subtopics in greater depth. This interconnected structure signals topical authority to search engines, improves internal linking, and creates a better user experience by organizing related content coherently. Topic clusters are especially powerful for agencies demonstrating expertise across complex service areas like SEO, AI optimization, and WordPress development.