What do you mean by 'virtual file system'?

Virtual File System (VFS) is an abstract layer that provides a unified interface for working with different types of file systems. It hides the details of specific implementations (such as ext4, NTFS, NFS) and allows the operating system and applications to work with files and directories in the same way, regardless of where and how they are physically stored.

For example, in Linux, VFS allows mounting different file systems into a single directory hierarchy, providing transparent access to local disks, network resources, and even virtual files (such as /proc). This simplifies development and maintenance, as applications interact with a universal interface rather than with each file system separately.