I have discussed the differences between audits, reviews, and compilations here and here. Even developed a visual illustration here. Ask any CPA and you can get a long explanation of the distinctions.
For something shorter, consult this article by Angus Loten in the Wall Street Journal, which said:
“An audit provides third-party assurance that a company’s financial statements are correctly prepared and based on verified business data, while a review shows the statements are at least internally consistent with data provided by management.”