Surge protector / SPD

A surge protector (or SPD — surge protective device) diverts or clamps transient voltage spikes so they don't reach and damage your electronics. There are two layers: a whole-home SPD wired into the distribution board handles the larger transients arriving on the mains and protects the whole installation, while point-of-use protectors (good surge strips/units at the socket) guard specific sensitive kit — TVs, computers, routers. The two work best together; a cheap surge strip alone offers limited protection, and quality matters (look at the joule rating/clamping spec, not just the word "surge"). Fitting a board-level SPD is a job for a licensed electrician, covered in more depth in the whole-home vs power-strips discussion.