Who is Purusha?

There is a creator deity, named Brahma. He is part of the Trinity: Brahma (creator), Vishnu (preserver), and Shiva (destroyer). Brahma is equated with Purusha as the first Cosmic Being. All things in the universe came out of him. He performed this act of creation by sacrificing the parts of his body (a thousand heads, a thousand arms, a thousand eyes, etc.) to become the world. For example, his breath became the wind. His feet became the earth. His mind became the moon. He is not changed into those things, but he actually is all those things, so everything that exists is sacred and divine. In a sense, no one sacrificed him--he sacrificed himself. But I know it is said that he was sacrificed by the gods. This idea of sacrifice became very important in the ancient Vedic rituals. There are many different aspects to this myth, and it can become confusing (for example there is a Mother Goddess who is also said to give birth to all gods), so try to keep your understanding simple. You can think of the many deities in Hinduism as different aspects of one Divinity.

Hinduism is not just one single religion, there are a number of different philosophies and schools of Hinduism, so it is more like a family of religions. That is why you read seemingly contradictory things, and different portrayals or definitions of Purusha.