A structural edit looks at the big picture of a manuscript, helping to shape the work to improve its organization and content. In fiction, this includes watching for continuity errors in plot, story and characterization. In non-fiction, this includes organizing the flow of ideas and identifying what can be fleshed out and what may be missing.
In general, a structural edit includes, but is not limited to:
Reorganizing the material to create coherent structure and flow
Expanding or reducing the material
Identifying missing or repetitive information
Managing headings and sections
Reorganizing information into different formats such as tables, charts or lists
Arranging placement of visual elements
A structural edit will not address specific issues with grammar and spelling, but will look at the manuscript's overall language, tone and word usage.