People use these terms interchangeably, but they describe two different ways of handling many claims at once, and the difference can affect how much say you have and what you recover. The simplest test is to ask whether your claim stays your own.
In a class action, a few representatives stand in for a large group and one outcome generally binds everyone. It fits situations where each person's harm is similar and often relatively small — the strength is efficiency, the trade-off is that individual members have limited control. In a mass tort, by contrast, each injured person keeps a separate claim. The cases may be coordinated before one court to resolve shared questions like whether a product was defective, but your own injuries, treatment, and damages still drive your case.
Why does it matter? Because in a mass tort your specific harm can affect what you recover, rather than a one-size-fits-all share. Which structure a given matter uses is generally set by how the litigation is organized, not chosen by you — and we can explain how a specific matter is set up, and what it means for you, in a free review.