Don't understand the difference between /lib and /include

The /lib folder states that it’s meant for private project libraries, but it also seems to me like the /include folder could be used very similarly, just that the /include folder should just be typically for headers. So would you make your header files in /include, and have your source files for them in /src? What is the main difference between /lib and /include

When a library, in lib, is being compiled, the include folder is not scanned for header files. For libraries in lib/mylib header and cpp filrs should, normally, be together - for example, mylib.h and `mylib.cpp.

The include folder is scanned when compiling your actual sketch files.

Speakinfg personally, my sketch’s cpp files, and header files usually all live together in src. I don’t use include. Other people keep cpp files in src and headers in include – PlatformIO gives you the choice.

lib is also where downloaded libraries are saved to. These are the ones mentioned in the lib_deps section of platformio.ini.