Learn in the textbookFile System Basics — Directory Management and Backup
DefinitionThe root directory (ルートディレクトリ) is the directory at the top of a hierarchical directory structure (階層型ディレクトリ構造), which organizes files in the shape of a tree.
ExplanationA directory is a container for files and lower-level directories, and since a directory can hold further directories, the whole structure forms an upside-down tree. Showing a location by writing the route from the root down to the target file is called an absolute path (絶対パス); because its starting point never moves, the notation stays the same wherever you are working.
AnalogyIf you write an address in full, from the region down to the house number, a letter reaches the same house no matter where it is posted from. An absolute path, written from the root, works the same way.
Memory hookA "root" is where a tree begins. Draw the tree upside down and the root ends up at the top.