Windows 10 20H1 Build to the Skip Ahead ring comes with a new feature designed to allow Insiders to access the Windows Subsystem for Linux (WSL) filesystem using the Windows Explorer. WSL is designed by Microsoft as a compatibility layer that makes it possible for Windows 10 and Windows Server 2019 to run Linux binaries in ELF format natively on their Windows computers. Windows Explorer support has been added by including a 9P server that comes with built-in protocols that support Linux metadata and permissions in the WSL init daemon.
Source: https://www.bleepingcomputer.com/news/microsoft/linux-subsystem-files-accessible-via-explorer-in-future-windows-10-releases/