TL;DR: Website structure refers to how pages are organized and linked together through hierarchy (URL folders/subfolders) and navigation (menus, links), which is essential for user experience, SEO, and scalability. The four main structure types are hierarchical (tree-like), sequential (step-by-step), matrix (multiple paths), and database (dynamic), with best practices including keeping content within three clicks of the homepage, grouping pages by purpose and subject matter, and creating comprehensive internal linking.