The word "Kundalini" means coiled and "Shakti" means energy. Ancient sages described Kundalini with the serpent. Kundalini yoga is an authentic spiritual practice that has been practiced for 2000 years or more. In ancient India, sages used to practice Kundalini yoga to discover the divinity within themselves.
All the techniques are recorded in Sanskrit scriptures called Upanishads. 20 Upanishads are there for the practice of Kundalini yoga. The translations are there in different languages. But you need to take an authentic book because there can be the possibility of miss interpretation.
Kundalini used to be secret before. It needed some qualification before. This serpent energy can be woken upward from your base chakra to the top by certain yoga postures, breathing, and mantra. Once chakras are opened, the energy moves upward and will be in ecstasy. Kundalini merges with pure consciousness, as a result the person will be enlightened.
What is serpent energy?
Where did this teaching first originate?
Many kinds of yogic practices can gain you enlightenment:
Kundalini yoga can be taken as visiting a pilgrimage. Each chakra can be related to one destination. For example, Sahasrara chakra to the Himalayas, heart chakra to Ganga like that. You need to start from your base chakra to Sahasrara chakra in correct order, worshiping each destination. You can refer to the image of the chakra for more details.
The energy flows through the Nadis. Often people think that Nadis are the veins or the nervous system, but it's not. They are non-tangible. For example, you can weigh your heart, but not your mind because it's not tangible. Similar way "Prana" which flow through the nadi is also not tangible.
Nadis are mentioned in all Upanishads, and the chakra is mentioned in 20 Upanishads. Nadi directs the flow of prana. Chakra serves different purpose. Many practitioners believe that chakra really exist in our body, and it really helps them to focus on that point well. The main purpose of the chakra is to focus on the point.
It doesn't matter if chakra really exist or not, but by focusing on that point and chanting the bija mantra, miracles can happen. Now the scientists have developed some machine to check the chakra is balanced or not in our body. I hope a day will come when science can explain these concepts and no one is skeptic about these subjects.
The Upanishads says: Kundalini can be awakened by agitating it, like hitting the snake with a stick. To awaken Kundalini there are a variety of asanas (postures), pranayama, bhandas. If you are more into the religious teachings and all, you may be thinking of shakthipath. It's fascinating that nowhere in Upanishads shakthipath is described.
No, Kundalini yoga is one of the step to reach enlightenment. Primary stuff is spiritual knowledge. Learning some spiritual information from internet or some source will not be helpful. Unless you really experience the truth yourselves, there is no use of any knowledge that you gain.
Experiencing a Kundalini awakening is something which I cannot tell you with my words. It's something different experience which each one need to experience. For example, the color of sky is blue. Can you explain the color to a blind person ? Certainly not. I guess you got my point.