It is a web-based tool that is used by the server administrators to manage hosting accounts on a web server. Ports 2086 and 2087 are used for WHM.Some of the tasks that a Server administrator performs on WHM are as bellow:

1- It is accessible by the root administrator.
2- users can also have access with the credentials of reseller.
3- Reseller/User have lesser features to operate on whic depends totaly on the server administrator.
4- We have a Reseller center where we can manage the resellers.
5-We can change the ownership of the account.
6-We have an option for configuring the cPanel cron jobs.
7- Maintenance operations such as upgradation and recompilation of PHP & Apache, installing Perl
modules, and upgrading the RPMs that are installed in the system.
8- Server administrator can delete , suspend and create a new cPanel.
9- Monitor the different sites with using different cPanel.
10-Ability to change the domain names of the clients.

Types of WHM:

1- Reseller WHM
2- Root WHM

Reseller WHM:

Reseller WHM are provided limited featured WHM

->Suspend, create and delete the cPanel accounts.
->Manage and monitor your sites (password resets).
->Access to all of your domains.
->Permission to check the server information and status.
->Access to customize your hosting and control panel (skeleton directory, branding).
->Ability to change your client domain names and usernames.
->But can not change the primary username.
->Can not install SSL certificates.
->Can not have permission to restart different services such as http, mail , sql and ssh.
->Resellers don't have the tool for automated backups.

Root WHM:

Root WHM have all the features inclusive of the reseller one

->Here we are able to change the primary cPanel username.
->Have the ability to install SSL certificates.
->Have permission to restart services (http, mail, sql, ssh).
->Have ability to assign IP addresses.
->Have the feature of automated backups too.
->Ability to change your client domain names and usernames.
->But can not change the primary username.
->Can not install SSL certificates.
->Can not have permission to restart different services such as http, mail , sql and ssh.
->Resellers don't have the tool for automated backups.

For more information:- click the link below

https://documentation.cpanel.net/display/ALD/WHM+Home+Interface