"Ha" means "sun" and "tha" means "moon," says Karen Fabian, a certified yoga instructor and owner of Bare Bones Yoga in Boston. Put them together, and you have a yoga style that focuses on balancing your entire body's energy as well as deepening the mind-body connection and stretching tight muscles via poses, deep breathing, and meditation, she says. You'll often start with a seated mediation and proceed into a slow, restorative, and relaxing flow that includes floor and standing poses, all the while using the classic "uijay" breathing (the type that sounds like you're imitating Darth Vadar) and sometimes props.
Find it: Although most yoga studios have a hatha class, you can also check out the Yoga Alliance school directory to locate one near you that uses this style.