Native development platform is intended to be used for desktop OS. This platform uses built-in toolchains (preferable based on GCC), frameworks, libs from particular OS where it will be run.
For more detailed information please visit vendor site.
Examples are listed from Native development platform repository:
; Latest stable version [env:latest_stable] platform = native board = ... ; Custom stable version [env:custom_stable] platform = email@example.com board = ...
[env:upstream_develop] platform = https://github.com/platformio/platform-native.git board = ...