Meaning of code once run anywhere?

Question

Cross platform

Answer 1

Platform independent

Answer 2

Basically this phrase is used for open source language like JAVA. The meaning of that is if the code is written by you once , you can run that code on any platform.

To write and run JAVA programs you require JVM and JRE (for more information you can Google it). The JVM converts the code we've written​ into a Non-Executable Byte code. A byte code is a highly optimized set of instructions. These byte code files can be run in different JRE (Java Runtime Environment). JVM will differ from platform to platform, but it will understand the byte-code. So you just need to install JVM based on your platform to execute the byte code on your machine.