The Aten is the god/embodiment of the sun. The hands of the Aten are stylized rays of the sun.
The Aten was the god worshipped by the Pharaoh Akhenaten, and thus became the god of all of Egypt. Until (and after) Akhenaten's reign, Egypt was a nation of many gods. However, during Akhenaten's reign, the Aten was the sole god worshipped, making Egypt a monotheistic country. Ahkenaten's son, Tutankhamun reverted the religion of Egypt back to a polytheistic religion.