Lazy loading means the browser only downloads an image when it's about to scroll into view, instead of all at once. That cuts the initial page weight and speeds up first paint.
The easy way
Add the attribute to your <img>: <img src="photo.jpg" loading="lazy" alt="..."> That's it — modern browsers handle the rest natively.
When NOT to lazy-load
Don't lazy-load images that are visible immediately (your hero or logo) — that delays them and can hurt your LCP score.
Lazy loading pairs best with already-small files. Shrink yours first with compress image or convert to WebP.