In computing, an inode (_index node_) is a data structure that describes a file-system object such as a file or a directory. Every file-system object on a Unix-style file system has one inode. The inode stores information about the object, including its size, permissions, and the time of its last modification.
Inode usage refers to the amount of space that inodes occupy on a file system. Inode usage is important because it can affect the performance of a file system. If a file system has too many inodes in use, it can become slow and inefficient.