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.
Of course, the job description should specify education, previous job experience, certifications and technical skills required for the role. You may also include soft skills, like communication and problem solving, as well as personality traits that you envision for a successful hire. While you may be tempted to list out every requirement you envision for your ideal hire, including too many qualifications and skills could dissuade potential candidates.