An inode is a record in a disk table, which contains information about a file or folder such as its size, owner, device node, socket, pipe, etc., except data content and file name. The number of inodes on your account equals the number of files and folders you have on it.
Registeram.com customers may see the number of inodes they are using from their account’s cPanel -> Stats -> Inodes Usage (situated on the left side on the cPanel home page). You may need to click on the Expand Stats link in order for the Inode usage graph to be displayed.
Every time a file is opened, the file’s inode is read by the kernel of the server. The more files/folders you have, the more inodes you use. And the more inodes you use, the more system resources your account consumes. That is why it is a common and necessary practice among hosts to limit the number of inodes on a shared server, where it is not suitable for one account to use system resources and leave no power for the other accounts.
In case your account reaches the maximum number of inodes, it may be excluded from the backup system, or you may experience problems with file uploading, receiving emails, and see errors when accessing your website.
Information on how to reduce the number of inodes your account uses can be found in this article:
How to reduce the number of inodes my account uses?