What is a class action lawsuit and what rights do class members have to opt out or object?

Under Federal Rule of Civil Procedure 23, a class action requires a sufficiently large group (numerosity), common legal questions (commonality), claims typical of the class (typicality), and adequate representation. In Rule 23(b)(3) damages class actions (the most common type), class members must be notified of the lawsuit and given an opportunity to opt out, meaning they can exclude themselves and retain the right to bring their own individual lawsuit. Class members who remain in the class are bound by any judgment or settlement. Members can also object to a proposed settlement at a court-supervised fairness hearing, and the judge must find the settlement fair, reasonable, and adequate before approving it. Attorney fee awards in class actions are also subject to judicial scrutiny.