The lawsuit filed by the Justice Department against Google on Tuesday marks the first major antitrust enforcement case against a technology company since a case against Microsoft began in 1998 and ended in a settlement with the government in 2002. The Justice Department is accusing Google of using anti-competitive business practices to maintain monopolies over its competitors in the online search and advertising industry, and Google is vowing to fight back, arguing that its success does not mean it did anything wrong.

Here are five key takeaways from Tuesday’s action:

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But Sarah Miller, executive director of the American Economic Liberties Project, which favors greater antitrust enforcement, called the consumer welfare standard “largely discredited” and said the Justice Department has clear authorization under the Sherman Antitrust Act of 1890 to take measures that would seek to ensure competition in the marketplace.

“Google maintains a 90 to 95 percent market share in online search,” Miller said. “It isn’t able to do that through designing a better product, it’s doing it by controlling the distribution channels and using monopoly profits to do so. So from a commonsense perspective, if you want competition in a market, the easiest way to do that is create more competitors.”