SvelteKit is a full-stack JavaScript framework that builds on Svelte to provide routing, server-side rendering (SSR), API endpoints, and deployment out of the box. It's similar to Next.js but with Svelte's simplicity and performance. The file-based routing system is intuitive: a folder src/routes/blog/[slug]/+page.svelte automatically creates a /blog/:slug route. API endpoints are defined with +server.ts files. Data is fetched in load functions that run on the server.