It is an important concept in Śaiva Tantra, where this force or power is believed to be associated with the divine feminine. This energy, when cultivated and awakened through tantric practice, yoga or meditation is believed to lead to spiritual liberation.
Kundalini can unwind from the base of the spine as a consequence of certain spiritual practices, or in response to life events. When this happens it can be moved little by little, unrolling like a snake, or quickly and explosively, involving the intestine, heart or head. This event can be surprising and chaotic, frightening or blissful, and usually triggers months and years of new sensations and changes in the person who awakens this energy.
That's why Kundalini awakening have to be done in a way that best fits your body and spirit.
You can find a well done and easy guide in "KUNDALINI AWAKENING: The complete guide to awaken your energetic potential, enhance psychic awareness, activate pineal gland, expande mind power, activate trascenence and higher consciousness" by Karen Cooper.
Here's what you will find inside the book:
the relationship between Kundalini and the seven main Chakras
prepare to awaken (physical symptoms, emotional symptoms, energetic symptoms and the desire to try something new)
Kundalini advanced yoga techniques
the practice of Tantra for Kundalini awakening
types of psychic abilities
and much more