From the story here:
Certifying the class allows any of the more than 200 groups that were subjected to the criteria to join the lawsuit. But until the IRS complies with the appeals court’s ruling this week, the list of those groups is secret.
Now that the class has been certified, the case moves to the discovery stage, where the tea party groups’ lawyers will ask for all of the agency’s documents related to the targeting and will depose IRS employees about their actions.
The lawyers hope they’ll be able to learn details Congress was unable to shake free in its own investigations.