Explainer-Why is the US suing Google for antitrust violations?

FILE PHOTO: A logo is pictured at Google's European Engineering Center in Zurich, Switzerland July 19, 2018 REUTERS/Arnd Wiegmann/File Photo

(Reuters) - The U.S. Justice Department and a coalition of state attorneys general on Tuesday will begin a blockbuster antitrust trial in Washington, alleging that Alphabet's Google unlawfully abused its dominance in the search-engine market to maintain monopoly power.

Here is an explainer on the key issues in the case.