What Is 360 degree feedback?
360 degree feedback refers to a process that is intended to improve individual and work-unit performance and productivity by collecting feedback from a range of people (subordinates, peers, customers and clients, managers) and making that "performance" information available to the individual to be used to learn to be a better performer at work.
It's called 360 because there are 360 degrees in a circle, and the idea is that the feedback should come from distinctly different sources, because each source type may have different (and valuable) information about how to improve performance.
Note that while the large majority of 360 degree feedback systems implemented today use a rating system, 360 feedback doesn't have to use ratings.