inode is a unix concept which means index node and represent a file internally. In short it is a it is a file structure on a file system except the file contents and the file name and used to track the file(s) stored on the disk. The inode entries store metadata about each file, directory or object, but only points to these structures rather than storing the data.
Content of the inode structure -
Inode number
Access Control List (ACL)
Extended attribute
Direct/indirect disk blocks
Number of blocks
File access, change and modification time
File deletion time
File generation number
File size
File type
Group
Number of links
Owner
Permissions
Status flags
