Performance appraisals are used to evaluate salespeople and are important for compensation, development, feedback, goal-setting, and other purposes. They involve evaluating salespeople periodically based on quantitative metrics like sales volume as well as qualitative criteria. The evaluations are most accurate when an immediate supervisor does them, criteria are appropriate, forms gather relevant information, and potential biases are mitigated. It is important to evaluate the entire performance appraisal system to ensure it meets the goals of both the company and salesforce.