The Gods of Olympus are an extra-dimensional race of beings who were worshipped as gods during the Ancient Greece. They no longer seek worshippers today, but they are still worshipped by the Amazons and Atlanteans.
The Olympians came into being from the effects of the Godwave energy spilled forth from the creation of the Fourth World, and came to power in the ancient world after overthrowing the Titans. This battle had weakened them and Hecate realized that if viewed as threat they would be a target of other gods of the universe. As a result she cast a spell that caused anyone that knew of them to believe they were much younger then themselves and therefore not worth bothering with.
However, Uxas came to Earth and told stories of their exploits to the inhabitants of Rome. This caused worship of the Olympians to increase so dramatically that to cope they split themselves into the Greek and Roman gods who eventually became separate beings. The Olympians realize that this had been part of a long time plan of Uxas to weaken them by dividing their overall power.
The Olympians played a role in the creation of the Amazons, who have been guided and protected by the goddesses ever since. By the modern day, some of the Olympians helped Diana, daughter of Amazon Queen Hippolyta, for her role in "Man's World" in which she became known as Wonder Woman. However, the God of War Ares saw the Amazons as a threat for their purpose of bringing peace to humankind contrary to his obsession with conflicts and has since plotted to destroying them.
Immortality: Every Olympian will never age.
Dimensional Travel: The Olympians can travel between Olympus and Earth, or send artifacts between them.
Only the power of the Olympian Gods can destroy the Mount Olympus.
Telepathy and Illusion Casting: Olympians can mentally communicate with their worshippers, transmitting their image at interdimensional range, and possibly can do the same to any other intelligent being.
Additionally, the Olympians have some power related to his/her individual sphere of influence: Dionysus, as god of wine, has full control of wine; Demeter, as goddess of agriculture, has total control of plants.
Power Loss: Olympian powers are dependent on the faith of their followers.
These characters are an adaptation of Gods of Olympus, characters in traditional stories. These include, but may not be limited to religious texts, myth, and/or folk lore. More information on the original can be found at Wikipedia.org.
In Rip Hunter #11, an alternate origin of the Greek gods posits they are merely aliens.