There can be some confusion around the various stages of publishing, and you might have seen the terms editing and proofreading used in similar ways.
These links can help clarify just what proofreading is and, on the lighter side, why it matters so much for your documents.
What is Proofreading?
Editors Canada – Standards for Proofreading
Society for Editors and Proofreaders – What is Proofreading?
Why Does It Matter?
The £8.8 Million Typo – The Guardian
The Comma That Costs 1 Million Dollars – The New York Times
Stock Trade Typo Costs Firm $225M – CBS News