Single Page Application
In plain terms
A web app that loads once and updates content without full page reloads.
Going deeper
An SPA fetches data and re-renders views client-side, giving app-like fluidity after the initial load. Navigation happens without round-trips to reload pages.
Under the hood
Fast interactions but heavier initial JS and SEO/initial-load challenges, addressed by SSR/SSG.
Examples
Gmail, Trello, React/Vue/Angular apps, dashboards, web tools.
Think of it like...
Like a kiosk that swaps screens instantly instead of reprinting the whole brochure each time.