Windows Shell Items (AKA "shellbags") is an undocumented set of structures used internally within Windows to identify paths in Windows Folder Hierarchy. It is widely used in Windows Shell (and most visible in File Explorer), both as in-memory and in-file structures. Some formats embed them, namely:
The format is mostly undocumented, and is known to vary between various Windows versions.
This page hosts a formal specification of Windows Shell Items using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.