The last three limbs of Ashtanga yoga -- dharana, dhyana (meditation) and samadhi (enlightenment) -- are collectively referred to as sanyam, which means "control." Patanjali explains dharana as the binding of attention to anything more than a single spot. He also states that the last three limbs should be considered together, as they are progressive stages of concentration.
Practicing dharana leads the practitioner to dhyana, which is the next stage of Ashtanga yoga. Dharana is the practice of concentrating on a particular subject, and dhyana is the state in which total concentration is achieved. This eventually leads to the eighth limb, samadhi, which is the deepest stage of concentration.
To practice dharana, the individual should choose a calm place and assume a comfortable seated position. The eyes can be kept shut to focus on a chakra or mantra, or they can remain open to fix the vision and mind on an external object. Beginners can practice dharana for about 10 minutes, then increase the duration as they advance.
Yoga can help an individual master the art of dharana because it involves focusing on the breath, body or even a mantra. Regular practice of dharana enhances yoga practice by improving the practitioner's ability to remain focused, no matter what they are doing. It trains the mind to remain calm and increases mental strength.