How it works
Both rely on proving that the app and the website belong to the same owner. On iOS you host a file named apple-app-site-association on your domain and list the domain in the app's Associated Domains entitlement. On Android you host a Digital Asset Links file, assetlinks.json, and declare the links in the app's manifest with automatic verification. Both files live under the /.well-known/ path of the domain. Once verified, tapping a matching link opens the app with no chooser dialog and no detour through the browser, and the app receives the full URL to route on.
Why it matters for an app team
Custom URL schemes can be claimed by any app and fail with an error when the app is missing. Verified links are safer, fall back to your website gracefully and stay clickable in places where custom schemes are not turned into links.
In practice
Example: https://example.com/product/42 opens the product screen for a user who has the app. For a user who does not, the same address loads the product page of the website, which can offer the app.
Common confusion
Verified links do not fire everywhere. On iOS a Universal Link typed or pasted into Safari's address bar opens the website, and some in-app browsers keep the user on the web page. A wrong or cached association file is a frequent reason why links silently open the browser. Neither mechanism handles users without the app; that takes deferred deep linking.