A WBFS file is a container file that stores Wii game data in a compressed and encrypted format. The file structure consists of several components:

The development and usage of files represents a pivotal era in the Nintendo Wii homebrew scene, fundamentally changing how users archived and played their game libraries. The Origins of WBFS

You shouldn't manage these files by hand. Dedicated managers like Wii Backup Manager or WBFS to ISO are essential for converting, splitting, and correctly naming files so the Wii can read them. Final Verdict