Editing: Edit means literally "to publish" (1791), possibly a back-formation from editor, or from French ?diter (which is a back-formation from ?dition). Another possible root of the word is in Latin: editus, past participle of edere "give out, put out, publish." From 1793 on, to edit means "to supervise for publication." From 1885 on, edit denotes "make revisions to a manuscript, etc." By 1960s, "an act of editing" became common in English.

Editing means selecting and preparing any form of media for before making it public. The word is commonly used in any industry that focuses on information -- from photography to movie industry. Accordingly, it is a quite broad term.

In the publishing industry, the term is used broadly to define the process of making a document or a text ready for publication by improving it in a variety of ways. Most of the time, editing is used as a substitute for copy-editing. 

Proof-editing: Let's admit: often, people or institutions who want to publish do not know what they want or what their text needs. Some texts are well-written: they need slight copy-editing or possibly only proofreading. Other texts, and this is often the case, are pretty problematic and need substantive copyediting. Proof-editing means having a look at the document to decide what the text needs. The client can then be informed about the necessary steps.

Copyediting: also known as copy-editing or copy editing, is the process of making it ready for publication in any form through small or large scale corrections. The process of copyediting involves making sure that whatever is published is accurate, easy to follow, fit for purpose and free of error, omission, inconsistency and repetition.

This process includes correction of the presentation of your content, structure, style, and flow of your text, omitting mistakes and analyzing the document structure for final publication. The step ''Copyediting'' is there clarify ambiguities and weakness in your text and polish its overall structure.

Proofreading: In the publishing industry, once the document is copyedited, the proof (or galley proof) that is being planned to be published needs to be checked to make sure that the text is ready for publication. Proofreading is having a last look at the document and making sure that all is fine with it before the text is finally published.

Proofreading includes extensive check and correction of the grammar, wording, spelling, punctuation, and grammatical inconsistencies in your document.

In the process proofreading, there are not many changes as in copyediting. Often, there is no re-writing of the material, because the process of copyediting has already handled the parts that need to be re-written.

Indexing: Everyone has seen a book which has an index at the end.
Even Shakespeare mentioned indexes: In Troilus and Cressida (I.3.344), he says,

And in such indexes, although small pricks
To their subsequent volumes, there is seen
The baby figure of the giant mass
Of things to come at large.

An index is an ''ordered arrangement of entries ... designed to enable users to locate information in a document or specific documents in a collection'' (ISO 999, 1996).
It is the list of words, names and subjects mentioned in the book or a document at the end. Usually, the list of entries helps the reader find the relevant information quickly without reading the whole book.

Indexing is the process of preparing the list of names and subjects in a book. As a sub-component of editing, it is quite different from copyediting or proofreading. Often, it requires the indexer to read the whole book and mark the parts that important words or names are mentioned.

Abstracting: It is the process of creating an abstract of a document or documents, often about a subject or group of related subjects. Related to indexing, abstracting makes it easier for people to have a rough understanding of large number of publications without having to read them.

Ghostwriting: The process of writing texts that are officially credited to another person. It is the process of authoring a text and giving credit of authorship to another person. Often, celebrities hire ghostwriters to write their biographies. Students or scholars in the academia hire ghostwriters as well to write their books, theses and papers for them. Ethically problematic, ghostwriting is a way of allowing someone else to benefit from the publication of a text in return for money.