Trimurti and Tridevi
Shiva and Vishnu are regarded as Mahādevas ("great gods" ) due to their central positions in worship and scriptures. These two along with Brahma are considered the Trimurti—the three aspects of the universal supreme God. These three aspects symbolize the entire circle of samsara in Hinduism: Brahma as creator, Vishnu as preserver or protector, and Shiva as destroyer or judge.
The Tridevi or triplet goddesses of Hinduism have equal importance as the trimurti. Brahma is creator, so he needs knowledge or goddess Saraswati (Vaak) to create. Vishnu is observer, so he needs the goddess of wealth and prosperity, goddess Lakshmi (Shri). Finally, Shiva is destroyer and re-creator, so he needs goddess Parvati, Durga, or Kali for power. They are the various manifestations of Goddess Adi Parashakti, the Supreme mother.
Read more about this topic: Hindu Deities