SPA Single-Page Application
A web app that loads once and updates via JavaScript instead of fetching new pages.
Classic sites: click a link → new request → new page. SPA: click a link → JS updates parts of the page → the URL changes via the History API but no full reload.
Good for app-like experiences (Gmail, Trello). Less great for content-heavy sites where SEO matters — there SSR or hybrids (Next.js, SvelteKit) are used.