In general, these are laws against things like war crimes. The UK (Brit here) also extends some child protection, fraud and bribery laws to cover acts worldwide, the former intended to be used to prosecute sex tourists who are unlikely to be prosecuted where they committed the offences.
I'm unsure whether any of these laws have actually specifically protected you, but the reason for their introduction is to afford people in other countries similar protection from UK-based criminals to the protections people enjoy in the UK.
Personally I hate whole "war crimes" thing. Since it WW2 it has been applied only to enemies. There was a lot of contention with the Russians over what was a war crime, since Stalin had done many of the same things as Hitler. It was generally agreed that it was only illegal when the Germans did it and Stalin went home happy.
It seems that Universal Jurisdiction allows people to prosecute me, but doesn't specifically protect me.
Yeah right.