The project scope statement identifies what will be done by the project. This result may only be described at a fairly high level. According to the PMBOK, it is "the description of the project scope, major deliverables, assumptions, and constraints."
The project scope description in the project scope statement can be progressively elaborated as the project proceeds. The elements of the scope are described in more detail in the project scope description than in the project charter. Components of the project scope statement include acceptance criteria, project deliverables, project exclusions, project constraints, and project assumptions.