The term “Hatha Yoga” originally referred to the practice of yoga poses (asana) and breathing (pranayama) in general. So, technically, any class that you go is hatha yoga class, (unless you don’t do any movement or breathing for some reason!).
However, in modern-day terms, “hatha yoga” describes a more classical style of yoga. Hatha-style yoga classes generally include postures that are held for a moderate length of time, with a focus on alignment and breathing. The pace of the class usually moderate, and will include postures that both stretch and strengthen the body.