Editing and Proofreading

Proofreading

Is the final and easiest stage of the writing/editing process which looks for cosmetic errors. It does not entail any reworking or rearrangement of content. 

Editing

Is about improving style, formatting, and accuracy by eliminating inconsistencies and ensuring that the style flows well. There are different levels of copy editing: light, medium, and heavy.

Heavy Editing

Includes restructuring some paragraphs, or heavily correcting style, flow, and grammar.

Medium Editing

Includes correcting flow and reworking some of the text.

Light editing

Might consist of double-checking accuracy and taking care of most grammatical issues.