Lazy Loading
In plain terms
Deferring loading of resources until they're actually needed.
Going deeper
Lazy loading delays fetching images, components, or data until they're about to be used, speeding initial load. It saves bandwidth and time.
Under the hood
Improves first paint and reduces payload; native loading="lazy" and dynamic imports implement it.
Examples
Below-the-fold images, code splitting, infinite scroll, route-based imports.
Think of it like...
Like only printing the chapters of a book as you reach them.