A Master Service Agreement (MSA) is an overarching contract that defines the broad terms and conditions applicable to any work a contractor may perform for a client. It typically outlines fees, scope of work, timeline, and other general guidelines. It establishes the legal framework the parties must abide by when engaging in future agreements or contracts.

A Statement of Work (SOW) is a specific, much more detailed agreement between two parties. It is typically used to supplement the MSA or other existing contracts, and goes into greater detail regarding the project scope, deliverables, timelines, cost, marketing activities, and other tangible elements. While MSAs establish the foundation of the relationship between two parties, SOWs provide details on how to execute the actual project(s).