Question

What do you mean by platform independence?

Answer 1

It means that the same program works on any platform (operating system) without needing any modification.

Answer 2

Software that can run on any hardware platform (PC, Mac, SunSparc, etc.) or software platform (Linux, MacOS, Unix, Windows, etc.). In general, programs written in Java language can be executed on practically every platform.

It depends on what you define as "the platform". In some cases this may be a specific hardware / machine configuration. In other gases in may be a "generic PC". In other cases it may be a virtual machine and runtime environment