A proofread is the lightest type of editing. It ensures that writing is free of strictly mechanical errors, such as spelling, punctuation, and grammar. It is usually the last step before a project goes to print.
Copyediting includes all the elements of proofreading, and it also works to improve phrasing, word choice, clarity, consistency, and organization.
Substantive Content Editing
Substantive editing includes all the above, and also involves some rewriting, as well as having a greater focus on the reorganization of ideas and text.
Depending on the level of edit requested, I will look for and correct:
Grammar and spelling
Consistency of capitalization and hyphenation
Overuse of adjectives and adverbs
Appropriateness of style and tone for the intended audience