Inode is single file, which in the server. It can be any file on your server including system files, emails, websites files, databases. Inodes are counted automatically and results are displayed at client area or in cPanel.
Inodes limit is counted only for Container and Storage VPS by formula:
Disk space (GB) x 15 000
With a minimum of 1000000 Inodes for VPS.
For cPanel hosting packages the limits are:
S10 – 100000
S20 – 150000
S40 – 200000
Usually these limits are more than enough for most websites. Most customers won’t notice this limit, because it’s way below what website needs, eg. default WordPress uses less than 1700 inodes.