A specific description of a unit of work activity that is a logical and necessary action in the performance of a behavior; how the behavior is demonstrated or performed in a particular context.
 
From PMS 310-1
 

Confirmation through the re-issuance of an incident qualification card that an individual has regained qualifications for a specified position that was lost through a lack of current experience. A key component in the certification or re-certification process is the subjective evaluation by the appropriate agency official of an individual's capability to perform in a position. 

A position-qualified individual who provides instruction to a trainee in the classroom, on-the-job, or on an incident. While many of the requirements of the trainer/coach are similar to the evaluator, it is important that the roles of training and evaluation remain separate. 

An individual who has met all required training and position experience for a specified position and is approved by their home unit's certifying official, to initiate a performance based training assignment in order to become qualified in the position.

A broad description that groups core behaviors necessary to perform a specific function.

An observable activity or action demonstrated by an individual in a particular context.

The process whereby the employing agency or contractor documents that the individual is fully qualified to perform duties and responsibilities for a specified position.

The individual who is qualified in the position being evaluated, or supervises the position being evaluated, having responsibility for observing task(s) being performed and documenting successful performance for agency certification or re-certification. Evaluator responsibilities must remain separate from the individual assigned as Trainer/Coach. 

The agency official at the home unit who is responsible for authorizing and granting position certification per agency policy. The agency official is responsible for completing the agency certification block located on the inside front cover of a Position Task Book. 

A document listing the performance requirements (competencies and behaviors) for a position in a format that allows for the evaluation of individual (trainee) performance to determine if an individual is qualified in the position. Successful performance of PTB tasks, as observed and recorded by a qualified evaluator, will result in a recommendation to the trainee's home unit that the individual be certified in the position.