Kali is one of the many forms of Shakti. Maha Kaali is the fiercest of all goddesses of Hinduism. The word Kali has its roots in the Sanskrit word "Kaal", which means time. And nothing escapes from time. Goddess Kali is sometimes referred as the goddess of death. But actually Kali brings the death of the ego. Even in the scriptures, she has killed demons but not anyone else. Kali is also not associated with Yama (the Hindu God of Death). Kali is considered a form of mother too. Maa Kali is one of the few Goddesses who are celibate and practice renunciation.
Goddess Kali and Lord Shiva, both are regarded to inhabit cremation grounds. Devotees go to these places to meditate with the purpose of overcoming the ego. The cremation grounds emphasize the idea that the body is temporary. Kali and Shiva are known to stay in cremation grounds because it is our attachment to the body that gives rise to the ego. Kali and Shiva give the idea of liberation by dissolving the illusion of the ego. The corporeal frame ultimately vanishes but the soul still remains. This is emphasized by the scene in the cremation grounds.
Goddess Kali has four arms and hands depicting her immense strength. In two of her hands, she holds a sword and a fresh severed head, representing a great battle in which she defeated the demon Raktabija. The other two hands are there to bless her true devotees, suggesting that they will be saved as she will guide them here and in the hereafter.