Shakti, power or force is the aspect of intensity, quantitatively, of being, while inseparable from it is the aspect of consciousness, qualitative or Shiva.
Shakti is feminine to the appearance of consciousness, which is masculine.
It connects the infinite to the finite.
It is reflected around us, it is the primordial substance of all that exists (Adi Shakti), it is the creative, fertile and regenerating power of life and it is reflected around us, in the outer world embodying the Eternal Feminine.
Shakti without Shiva is Shava or corpse and Shiva without Shakti is an unstructured scientific force.
Shakti is so responsible for creation and is the agent of all changes or transformations. Shakti is cosmic existence, as well as liberation, its most important form being kundalini Shakti, a fundamental, mysterious and overwhelming inner psychospiritual force.

In Shaktism and Shaivism, Shakti is revered as the Supreme Being. Shakti embodies the active feminine energy of Shiva and is identified as one of the 10 Great Divine Powers MahaVidya or as Parvati, the female counterpart of Shiva.

David Kinsley mentions it as The "Shakti" of the god Indra as Sachi (Indrani), which means power.
Indrani is part of a group of seven or eight mother goddesses called Matrikas (Brahmani, Vaishnavi, Maheshvari, Indrani, Kumari, Varahi and Chamunda and/or Narasimhi), who are considered to have the Hindu gods major shaktis (Brahma, Vishnu, Shiva, Indra, Skanda, Varaha/Yama and Devi and Narasimha respectively).

The goddess Shakti is also known as Amman (meaning "mother") in southern India, especially in the states of Karnataka, Tamil Nadu, Kerala, Telangana, and Andhra Pradesh. There are many temples dedicated to the different incarnations of the goddess Shakti in most of the villages of southern India. Rural people believe that Shakti is the protector of the village, the punisher of bad people, the healer of diseases, and the one who gives wealth in the village. They celebrate Shakti Jataras with great interest once a year. Some examples of incarnations are Ganga Ma, Aarti, Kamakshi Ma, Kanakadurga Ma, Mahalakshmi Ma, Meenatchi ma, Manasa Ma, Mariamman, Yellamma, Poleramma, Gangamma and Perantalamma.

According to some schools, there are four Adi Shakti Pitha (places of worship for the primordial Shakti) and 51 centers of Shakti worship located in South Asia. They can be found in India, Sri Lanka, Nepal, Bangladesh, Pakistan and Tibet.
They are called Shakti Peethas.
The list of locations varies. A generally accepted list of Shakti Peethas and their temple complexes includes:

Hinglaj Mataji Balochistan
Jwalaji (Himachal)
Tarini Country (Brahmapur, Odisha)
Katyayani (Chattarpur, Delhi)
Bhadrakali (Kodungallur, Kerala)
Kamakhya (Assam)
Kali at Kalighat (Kolkata, West Bengal)
Naina Devi (Himachal)
Guhyeshwari Temple Devi (Kathmandu, Nepal)
Ambaji (Gujarat)
Vishalakshi Temple (Varanasi).

Other pithas in Maharashtra are:

Tuljapur (Jagdamba)
Kolhapur (Mahalaxmi)
Vani-Nashik (Saptashrungi)
Mahurgadh (Renukamata)

Adi ParaShakti, whose material manifestation is Tripura Sundari, is a Hindu concept of the supreme Shakti or MAHASHAKTI, the supreme power inherent in Creation. This perspective is particularly prevalent in shakta, the perspective in which devotees adore the Goddess-Devi in all her manifestations.

Smarta Advaita is a branch of Hinduism in which Shakti is considered to be one of the five personal facets of God in the panchadeva - the system supported by Adi Shankara.

Quotes from Shaktisangama Tantra:

"Woman is the creator of the universe, the universe is her form; The woman is the founder of the world, she is the true form of the body.

" Woman is the form of all things, of everything that lives and moves in the world. There is no rarer jewel than a woman, nor a condition superior to that of a woman."