Inodes represent the amount of all the files and directories located on your hosting account. For example, an image will be 1 inode. An email message which contained 2 attachments will be 3 inodes. Any image file, video, HTML file, folder and script file are considered inodes.
To check the current inode usage on your account, go to Websites → Manage, search for Order Usage on the left sidebar and click on it:
You will see two charts. The one to the right indicates the current amount of inodes used and the inode limit of your account:
What happens if the inode limit is reached?
Once the inode limit is reached, you will no longer be able to create any additional files. Your website might also stop working properly. The solution is to remove any unused website files (logs, uploads, images).