Copy Editing, Stylistic Editing, & Line Editing
Line-by-line editing ensures a document is clear, correct, consistent, and concise. Copy editing is mechanical, line-by-line editing that corrects grammar/usage, punctuation, and spelling errors. Stylistic editing is non-mechanical line-by-line editing that involves revising the manuscript for coherence, flow, jargon-removal, repetition, and language smoothing. For me, light editing focuses on the mechanical issues, while heavy editing includes both mechanical and non-mechanical revisions.
Also called content editing or structural editing, substantive editing involves clarifying and reorganizing manuscripts for both structure and content. By focusing on the document's intended audience, the substantive editor seeks to improve readability, comprehension, clarity, and organization. This kind of editing focuses on the big picture, rather than the line-by-line changes of copy or stylistic editing.
A manuscript critique is a kind of substantive editing that involves reading an author's entire manuscript and offering an educated outsider's opinion on the work. At this stage, the editor tries to preemptively ask the questions a confused reader might ask, so the reader never has to ask them. The author will receive detailed feedback in the form of an editorial letter.
Proofreading is the final edit a document goes through before publishing. At this stage, all copy edits and stylistic edits are complete, and the proofreading editor searches for typos and mistakes that have slipped through (or have been introduced by) earlier revisions.