What’s the deal with the & project folders?

1

I’ve latest versions in my toolchain (ESP32 xtensa compiler). A good concise breakdown of how the folders will behave consistently would be greatly appreciated.

2

src → contains your source code (.c / .cpp maybe even .h files)
include → This directory is intended for project header files.
lib → This directory is intended for project specific (private) libraries.
test → This directory is intended for PlatformIO Test Runner and project tests.

See the README inside the respective folder.

But how is your question related to the latest toolchain version you mentioned?
Usually you use the toolchain which is bundled with the respective platform!?