Hi,
A job description is basically the duties and responsibilities designed for a specific post. It describes the nature of duties and responsibilities, reporting structure, qualifications, and experience required to perform the job, etc. A job specification is mainly concerned with the performance of the job. It includes skills, knowledge, abilities, attitudes, etc. A job description is a standard, whereas job specification varies from person to person. A job description is done to define the outline structure of the job in a department, whereas job specification is mainly done to evaluate the person for performance appraisal, training needs identification, etc.
Suresh