What does WORA of java actually means. What does different platforms mean??

Answer 1

WORA of Java means

"Write Once Run Anywhere"

Java is the only programming language which had this feature when java was actually released, I don't think that if still it is the only language having this feature.
What it does is that you need to compile your code once and you can run that code in any other platforms or OS. This can' t be done in other languages as they are "compiler dependent" while Java is "compiler in-dependent".

Other Platforms means other devices, I mean like Windows and Mac are separate platforms likewise android and ios are separate platforms, I hope you have understood.

Answer 2

this became possible because of JVM, note that java by itself couldn't be platform independent , so what sun microsystems people did was,
they made platform specific JVMs(it actually runs your java code on any system) for different types of platform which can now run java on any device.

hence java is platform independent , uses bytecode.
but JVM that runs java is platform dependent converts bytecode to machine understandable form