Developmental editing is typically focused on the content, premise, structure, and story of a manuscript rather than its wording. There is a good deal of editorial feedback given, but it is usually more conceptual in nature and focused on helping you first identify the best goals and priorities to maximize a work’s potential and then to support the revision effort at the highest level possible.
Line and copy editing is focused almost exclusively on your prose style, narrative voice, and then finer details of grammar, spelling, punctuation, formatting, and in many cases conformity to a specific style guide such as The Chicago Manual of Style.