MIPS is a system developed to reduce concussions. It is based in allowing some movement of the helmet to reduce the inertia on the brain. A regular helmet is very effective at protecting you from cranial injuries, but not so from concussions which happen when your brain slams into the cranium due to inertia.

MIPS attempts to address concussions while still protecting from skull fractures. It appears to be based on some sound science and has gone through quite a bit of testing -go to the MIPS website for details. But only time will tell how effective it really is.