Proofreading (also proof-reading) is the reading of a galley proof or computer monitor to detect and correct production-errors of text or art. Proofreaders are expected to be consistently accurate by default because they occupy the last stage of typographic production before publication. wikipedia.org

Copy editing (also written as copy-editing or copyediting, and sometimes abbreviated to ce) is the work that an editor does to improve the formatting, style, and accuracy of text. Unlike general editing, copy editing might not involve changing the substance of the text. wikipedia.org

Technical editing involves reviewing text written on a technical topic, and identifying usage errors and ensuring adherence to a style guide.