How to delete a project (without content

There are folders and projects … a project seems to be a folder +

I know what a project is supposed to be …
Can someone explain the concept and explanation of a project in programIO ???
erases existing projects , seems not thought through

Folders are part of your file system… a project is a collection of specifically named folders, with a platformio.ini file to configure the project and tie everything together. If you want to delete a project entirely, just delete the whole folder.

i.e. you will typically have at minimum a folder containing all your project stuff, with a src subfolder which contains all your source files, and a platformio.ini telling PlatformIO what platform, framework, board, libraries, etc your project needs. When you create a project in PlatformIO, you also get some other folders just in case. You might have some private libraries (which you’d place in the lib subfolder), unit tests (test subfolder), or header files for reusable code (include subfolder), etc, etc.

Not sure what you mean there?