
In Hatha Yoga , Ida Nadi represents the negative force, the flow of consciousness , pingala represents the positive force ,the flow of vital energy ,and sushumna nadi represents the neutral force, the flow of spiritual energy .
The union, the connection between these three flows occurs in ajna chakra ( the eyebrow centre ). Therefore union between ida,pingala,sushumna is hatha yoga.When this union ,takes place there is an instant awakening in mooladhara chakra at the base of spine .This is the Kundalini Shakti .The awakening of Kundalini is the subject matter of Hatha Yoga .Through the practices of Hatha yoga ,there is a union .As a result of that union ,the awakening of Kundalini takes place .When awakening occurs, then Kundalini ascends to higher realms of consciousness and finally it reaches in Sahasrara Chakra (crown chakra ).
When Kundalini is established in Sahasrara chakra ,that is called YOGA ,not Hatha Yoga .This is the difference between Yoga and Hatha yoga.
Yoga means union of Shiva (Consciousness) and Shakti (energy).
Shakti is Kundalini energy ; Shiva is the supreme consciousness in Sahasrara Chakra . When awakening takes place in mooladhara (at the base of spine ),then Kundalini starts ascending .
She ascends through sushumna ,not through ida and pingala. Sushumna is the highway for Kundalini .It passes through various chakras , sometimes all of a sudden and sometimes very slowly. When it unites with ida and pingala in ajna chakra ,that is called hatha yoga .Then ,after this first union ,it forges ahead to sahasrara chakra .There it unites with the supreme consciousness,Shiva .That is called Yoga ,which means ultimate union .
Therefore , the ultimate object of Hatha Yoga is to experience yoga .