90/360/720 degree performance appraisal - Is there more of this type of Performance Appraisal Method?

shijit
Friends, We have heard about different degrees of Performance Appraisal Methods. Can someone clarify what this degree represent? Why its called 360 degree, 90 degree or 720 degree? Is there more of this type of Performance Appraisal Method? How 360 degree appraisal is different from other degrees of the Performance appraisal method? Please clarify this doubt if you know.
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