performance is about behavior or what employees do, not about what employees produce or the outcomes of their work. Performance management systems typically include the measurement of both behaviors (how the work is done) and the results (the outcomes of one's work). Performance is evaluative and multidimensional.
There are two important facets of performance: task and contextual. Task performance refers to the specific activities required by one's job. Contextual performance refers to the activities required to be good "organizational citizen". In addition, voice behavior is another important facet of contextual performance. Both task and contextual performance are needed for organizational success, and both should be included in a performance management system.
Employees do not perform in a vacuum. Employees work in a specific situation, engaging in specific behaviors that produce certain results. An emphasis on behaviors leads to a behavior-based approach to assessing performance. An emphasis on the employee leads to a trait-based approach to assessing performance. The relative emphasis given to each of these approach to measuring performance should be influenced by the organization's business strategy.