While many people use the terms job description and job specification interchangeably, there's a difference between the two. One tells what the job entails, while the other tells what qualities the individual filling the job needs to have.
A job description is a written statement describing the general responsibilities and duties of a given position. It should be considered an advertisement for the job as it often lists the results expected from the person in the position and tells to whom the person reports. It may include general working conditions as well. A job description can also be used as a benchmark for bosses to evaluate current employees.
A job specification normally provides a list of the qualifications anyone filling the post should have. These qualifications might include necessary education, previous work experience and specific skills needed for the position.
The term job analysis is often used along with the terms job description and job specification. A job analysis determines the exact duties performed as part of a particular job. The analysis also determines the employee qualifications and skills necessary to fulfill the job requirements.