Cross-platform app
An app whose single codebase runs on both iOS and Android.
Glossary · Apps & products
A cross-platform app is built with tools such as React Native or Flutter: most of the code is written once and runs on both platforms.
That shortens development and simplifies maintenance, because a fix is made in one place. But “one codebase” does not mean “half the price”: each platform still has to be tested separately, and the app stores have their own requirements and review process.
The limits show when you need the newest platform features or complex work with the device. In that case part of the code is written natively anyway.