Think of this as describing the purpose of the position, and its role within your company or organization as a whole. A job summary will briefly acknowledge the fundamentals of the position, so leave space on your job description template to answer.
Typically, organizations use their human resources or personnel department to create job description templates. In some cases however, a departmental group, a manager, or another individual (usually the direct supervisor of a position) might be responsible for creating one. In any case, make sure the creator of the template is familiar with the company’s or organization’s needs.