Surge protection saves equipment from damage caused by lightning and voltage irregularities called spikes and surges. See C-band Surge Protection.
A power bar with surge protection will absorb any power surges (from lightning, power spikes, etc.) without damaging the computer equipment. Without surge protection, these power problems can damage the computer.
The process to reduce voltage surges that may occur as a result of lighting or a power supply surge which can produce more than twice the voltage normally expected from the power source.