"Let us realize the arc of the moral universe is long but it bends toward justice."
Dr. Martin Luther King, Jr.

What is a class action in the United States?

A class action lawsuit occurs when a court combines the grievances of at least 40 different people into one civil action because they share at least one common issue of fact or law. It is a procedural mechanism. Any party can file a class action complaint but only a court can decide whether it should be certified as a class action. If a court refuses to certify a case as a class action, then the client may proceed with the case on her on behalf or she may withdraw the lawsuit. Class actions may be brought for almost any violation of substantive law, such as federal securities fraud statutes, consumer protection statutes, common law or statutory fraud, breach of contract, federal laws forbidding employment discrimination on the grounds of race or sex or national origin, antitrust (or competition law) violations, and other matters. Class actions are available in federal courts under Federal Rule of Civil Procedure 23; Rule 23 was originally designed in the 1960s to make it easier for people to obtain compensation for injuries caused by racial discrimination. Class action procedures are also available under most state rules of civil procedure for cases filed in state courts.

A class action saves court time and allows a single judge to decide upon similar issues of fact and/or law at the same time, resolving common issues at once for as many as hundreds or thousands of people with the same grievance. If a court agrees to certify a complaint as a class action, everyone with the same grievance may become a “class member” or a “member of the class” with the same rights before the court. In a class action, one person, usually called the “lead plaintiff” or “class representative” or “named plaintiff,” represents everyone who suffered similar harm from a defendant’s unlawful conduct. Class actions play an important role by representing the interests of people who would otherwise not bring a lawsuit because it would be impractical or prohibitively expensive for each person to file an individual lawsuit, particularly over small claims. Class actions enable shareholders or consumers to seek recovery from large corporations with greater legal and financial resources. 
They also enable employees who were paid less than other employees due to their race or gender to join together in a lawsuit against the employer. The typical class action may take 2-3 years to resolve, but the actual time varies with each case.