360 degree feedback is an overall feedback process assessed by your seniors, peers and even by customers. They evaluate by going through your performance report (whether you have achieved your KPI), personality and value addition to the organization.
You receive an analysis about yourself through an outside perspective and how professionals perceive you.
A 360 degree overview helps an individual in improving his work, personality and increases healthy communication among team members.
A word of caution for assessing 360 degree feedback is that one must not link this assessment with performance appraisal as it may lead to biases.
Thus, a constructive feedback like this one should be taken in ones stride.