Proofreading
The last step before publishing
Corrections in spelling, grammar, punctuation, and typography
Checking obvious facts
Checking style guides and maintaining consistency

Copy Editing
Correcting typos, basic grammar, punctuation, word usage
Making style consistent: spelling, capitalization, hyphens, dashes, italics, ellipses, etc.
Flagging content inconsistency
Maintaining style consistency and language style
Verifying basic facts
Flagging plot holes, potential libel, potential copyright issues, confirmed anachronisms, and repetition (both content and verbal)
Flagging ambiguous vocabulary, awkward phrasing, and jargon and making suggestions
Flagging repetition and making suggestions

Line Editing
Copy editing
Suggesting improvements to word usage and scholarly tone (in the case of academic texts)
Addressing issues with flow, tone, clarity, and language
Flagging plot holes, potential libel, potential copyright issues, confirmed anachronisms, repetition (both content and verbal) and making suggestions
Correcting issues with coherency, repetitive word use, redundancy, and ambiguity
Basic formatting