The Hatha Yoga Pradipika (ancient text) is the first written book on asana (postures) that were designed to purify the body and prepare the body for meditation. Before Hatha Yoga there was no physical movement (postures).
Hatha Yoga is a thoughtful practice where we use the body to connect with the breath and then the mind. In this practice we may move slower or differently than in a Vinyasa practice using many of the same postures you may have experienced before.
Hatha Yoga can be purifying, strengthening, grounding and build internal heat. Each teacher will have their own way of teaching this traditional yoga practice.