Nadis
Prana means life force, cosmic energy, wind and power. There is, in yogic thought, no distinction between the breath of an individual and of the pulsation and movement through the cosmos.
The pathways for energy to travel are called nadis, which means movement or stream. On a gross level these nadis correspond to the veins and arteries that carry blood through the body as well as the nervous and lymphatic systems. On a deeper and more subtile level, the nadis channel the flow of prana.
There are perhaps thousands of nadis traveling through the body, though for the yogi, three main nadis are of importance. These are the sushumna, pingla, and ida (pronounced eda)
The sushumna nadi is the main channel, and is often referred to as the most gracious channel. Here, energy is moved through the central axis of the spine starting at the base and traveling up to the crown.
the pingla and ida form a double helix around the sashumna nadi, intersecting the chakras along the way.
The pingla, also starting at the muladhara chakara, spirals up the spine ending at the right nostril. It corresponds with the sympathetic nervous system, is associated with the sun, and is masculine by nature. This channel, when activated is warming, and good when action is needed.
The ida, starts at the svadisthana chakra and spirals up to the left nostril. It corresponds to the parasympathetic nervous system, is associated with the moon, and is feminine by nature. When activated, this channel is cooling, calming and brings equilibrium and steadiness. This sets up a good space for meditation.
There are many pranayama (breath control) techniques that can activate the nadis, and bring specific results, though the main objective is to cultivate energy, and increase life force.