A Scope of Work (or sometimes called a Statement of Work or SOW) allows you to clearly define the who, what, where, when, why, and how projects, jobs or activities will be completed. The SOW defines contractual expectations, the activities that will take place, a reporting structure, timelines to complete each activity, response time, pricing structure and any conditions or restrictions.
While most vendors commit to the SOW and follow it to the letter, they will not allow for much, if any, flexibility, even during times of change. Your ability to work with a vendor that allows you to adapt the SOW to put your needs first and flex over time will give your business a competitive advantage.