Android is the Google developed operating system for mobile phones and tablet devices. Built on top of a Linux based core, Android uses Java as the native language for all of it's mobile apps. Native Android app development is done with Google's freely downloadable Android Studio application. Unlike Apple iOS's compiled Objective C applications, Android uses a virtual machine to run it's native apps.
Google allows developers to more freely interact with their devices than Apple's closely guarded, proprietary platform. Developers can build and distribute test builds to QA testers and clients without the need for a 3rd party service like Testflight. This makes QA and User Acceptance Testing much easier, and rolling out incremental builds faster.
Application development done for Android is not cross-compatible with Apple devices. Projects that are looking to target both Apple and Android devices with native applications will need to write and test two separate projects. This will allow a project to squeeze the maximum amount of performance and functionality out of the platform. Not all applications require this level of effort, and you might be better served with a cross platform development tool.
For projects that do not need to push the limits of the hardware, using a cross-platform framework will allow you to multiply your development effort across both Android and Apple devices. We use Cordova and toolsets built with Cordova like Quasar and Ionic. These allow developers to use the Webview object, available in both iOS and Android, to run a web application designed to deliver mobile application features.