Hatha in Sanskrit literally means ‘stubborn’. So Hatha Yoga practice means the stubborn practice of yoga, without the interference of the five senses and the mind. Generally, people think of Hatha Yoga only as asana practice. But it is the austere practice of asana, pranayama, dharana, and dhyana to achieve the sublime state of samadhi. In samadhi the yogi becomes free from the illusion of form, time, and space. Asana is just one of the six practices in this path.
Hatha Yoga originates from Raja Yoga. It is the simpler version (without Yamas and Niyamas) of Raja Yoga. In simple words, you can say all the yoga poses and pranayama exercises can be classified as Hatha Yoga. So if you practice any yoga asanas or pranayama exercises you are practicing Hatha.
It is interesting to know that some teachers explain Hatha as Ha (sun) + Tha (moon) yoga, because of the fact that Hatha Yoga helps to purify our solar (Pingla) and lunar (Ida) channels.
Hatha yoga is the branch of yoga that typically comes to mind when you think of yoga in general terms. The practice involves breath, body, and mind, and classes are usually 45 minutes to 90 minutes of breathing, yoga poses, and meditation.