Surge can be caused for example, by lightning striking near your premises. Lightning induces voltage surges in conductors and cables that can damage any connected equipment. Also switching in households, for example with fluorescent light fixtures and conventional magnetic ballast, can cause surges in the house wiring system.
Surge protectors are not really protectors against lightning but rather surge suppressor, there is no device to protect a homeowner against direct lightning strike. The best protection is unplug all electronic equipment during thunderstorm.
Any suppressor device will provide some degree of protection from every power line spikes and distant lightning strikes.
I found from my experience that surge “protectors” breakers are also very good in stabilizing voltage in building and thus fixing problems with reverting electronic clocks, or malfunctioning electronic equipment.