A native app is an app that is developed for one particular operating system (e.g. iOS or Android) only.
Native apps are usually downloadable via app stores like the Apple App Store or Google Play Store.
Native apps (compared to web apps) can take full advantage of the device's features like camera, vibration, and GPS. After the download, they are shown as an icon on the home screen of the mobile device.
Native apps have better control over the orientation, size, and resolution of the app. Developers have access to layout features that help them in their development. They can specify the screen size and aspect ratio. The mobile app then maintains the aspect ratio on other screen sizes.
The maintenance costs of a native application are also relatively high, accounting for 15-20% of the development costs.