Short answers, pulled from the story.
The word Brahma appears in the Maitrayaniya Upanishad, a text likely composed around the late 1st millennium BCE. This early scripture maps the concept of Brahma to one of three qualities known as Gunas, specifically Rajas or passion.
Traditional depictions show Brahma as a red or golden-complexioned bearded man seated upon a lotus flower with four heads pointing toward the four cardinal directions. He possesses four arms holding specific symbols including the sacred Vedas, a mala representing time, a shruka ladle for sacrificial fires, and a kamandalu water pot symbolizing the source of all creation.
By the 7th century CE, Brahma had lost his significance compared to other major deities like Vishnu and Shiva due to the rise of Shaivism and Vaishnavism which replaced him in many traditions. Legends explain this lack of active worship through stories of dishonesty during a debate between Brahma and Vishnu where Shiva cut off one of his five heads for lying about finding the beginning of a cosmic fire column.
The most prominent temple is the Brahma Temple located in Pushkar, Rajasthan while other shrines exist in Asotra Barmer, Khokhan Kullu, Nagargao Valpoi, Chhinch Banswara, Khedbrahma Sabarkantha, Bithoor Kanpur, Thanjavur Tamil Nadu, Chebrolu Andhra Pradesh, and Mangalwedha Maharashtra. A shrine also exists at Kandiyoor Mahadeva Temple where Lord Shiva beheaded Brahma and statues stand at the Erawan Shrine in Bangkok Thailand and Cambodia's Angkor Wat.
Brahma functions as the Creator within the Trimurti alongside Vishnu the Preserver and Shiva the Destroyer. Post-Vedic Puranic literature offers multiple theories regarding how this trinity formed including claims that Vishnu created Brahma from a lotus emerging from his navel or that they cyclically create each other across different cosmic aeons known as kalpas.