3 AnswersNew Answer
I believe cross platform means that your app or code can run or work on multiple devices and operating systems. For example, the Facebook App can work on Android, Apple, Linux, Windows , etc without any problem. So when coding you must ensure this before you release your app/ software / website.
In computing, cross-platform software (alsomulti-platform software or platform-independent software) is computer softwarethat is implemented on multiple computing platforms. Cross-platform software may be divided into two types; one requires individual building or compilation for each platform that it supports, and the other one can be directly run on any platform without special preparation, e.g., software written in aninterpreted language or pre-compiled portablebytecode for which the interpreters or run-time packages are common or standard components of all platforms. For example, a cross-platform applicationmay run on Microsoft Windows on the x86 architecture, Linux on the x86 architecture and macOS on either the PowerPC or x86-based Apple Macintosh systems. Cross-platform programs may run on as many as all existing platforms, or on as few as two platforms. Cross-platform frameworks (such as Qt, Xamarin, Phonegap, or Ionic) exist to aid cross-platform development. https://www.google.com/url?sa=t&source=web&rct=j&url=https://en.m.wikipedia.org/wiki/Cross-platform&ved=2ahUKEwiA7vyg3-3ZAhUBLY8KHQEdBxgQFjAAegQIBhAB&usg=AOvVaw3C9ZxrnuwKy1tohmHsZCBA
any easy way to make cross-platforms