Hinduism has no central dogma and no single founder; it is not polytheistic; it is henotheistic. It is an umbrella term for a wide range of beliefs and practices, including various schools of philosophy, Vedic rituals, Yoga, and meditation. The earliest surviving literature on Hinduism comes from the Rigveda, dated to 1700 BCE, but the religion itself is thought to date back to at least 2000 BCE when Indo-European tribes migrated into the Indian subcontinent from Central Asia.
Hindus believe in one supreme god (Brahman), but they don’t believe that only one god exists. Instead, they believe that there are many gods and goddesses who represent different aspects or forms of Brahman. So while Brahma may be considered Brahman’s physical form, Vishnu might be considered Brahman’s mental form and Shiva might be considered Brahman’s spiritual form.
The Trimurti is the Hindu triumvirate of those forms. It represents the three primary functions of God: creation (Brahma), preservation (Vishnu), and destruction (Shiva). The Trimurti also represents three aspects of human life: birth (Vishnu), life (Shiva) and death (Brahma).
For example, if you are looking for protection from danger or illness, you might worship Durga or Kali because they stand for strength and power. If you want to pray for success in your business ventures or job interview, you might choose Lakshmi because she represents prosperity and wealth.
There are many other gods and goddesses that either represent different aspects of Brahman or represent other ideas and concepts.