Officials promised to "seek redress" if they found something offensive. Wall Street Journal sources claimed that DOJ would not ignore violations of other laws if they were discovered during the review.
The department did not mention specific goals, but it is not difficult to guess which tech giants are likely to come under the chairs. Amazon, Apple, Facebook, Google and Microsoft all have tremendous influence on the internet, although they do not always have a monopoly on a given site.
And those companies are likely to be nervous. They have already been asked to testify before the Congress on Competitive Issues, and reports have sent out about regulatory authorities that have overseen the oversight of Amazon and Google ahead of seemingly probable actions. It does not include an impending Facebook settlement with the FTC. There is a real chance that they will be asked to change practices or even divide into several companies.
You know that these companies will also create tough resistance. Apple has already denied that the App Store is a monopoly, and companies like Google have typically argued that you are not locked in to using their web services as you may be with software. They are determined to maintain the status quo and they know that the consequences of losing can be serious.