The WHM offers you two options to have the server rebooted:

Forceful Server Reboot
Graceful Server Reboot

If you are planning to reboot the server it is recommended to use the graceful server reboot. The graceful reboot allows the server to close any user-level running processes before restarting.

The forceful reboot can result in data loss, however if your system will not do a graceful reboot this is generally preferable to a hard reset.