The platform guide

By the end of this book, we will be building apps that are ready to be deployed on the device. Since Cordova takes HTML, CSS, and JS code as input and generates a platform-specific installer, we need to have the build environments available on our machine.

Android users can follow the instructions in the Android Platform Guide at http://cordova.apache.org/docs/en/edge/guide_platforms_android_index.md.html#Android%20Platform%20Guide to set up SDK on your local machine.
iOS users can follow the instructions in the iOS Platform Guide at http://cordova.apache.org/docs/en/edge/guide_platforms_ios_index.md.html#iOS%20Platform%20Guide to set up SDK on your local machine.
You would need an macOS environment to develop iOS apps.

As of today, Ionic supports only Android 4.0+ (although it works on 2.3 as well) and iOS 6+ mobile platforms. But Cordova supports a few more.

You can check out the other supported platforms at: http://cordova.apache.org/docs/en/edge/guide_platforms_index.md.html#Platform%20Guides.