The Greeks are the first civilization used in the Age of Mythology campaigns. You start out with them in the "Fall of the Trident" and "Learn to Play" campaigns.
Their major gods are Zeus, Poseidon, and Hades, and their minor gods are:
The Greeks gain favor by praying at a Temple. When a Greek Villager finishes building a temple, he or she will automatically start praying there to accumulate favor.
Greek units tend to be the toughest for their type - a Greek Hoplite is better than an Egyptian Spearman or a Norse Ulfsark - but also the slowest and most expensive. A Spearman travels at 5 meters/second, but a Hopite travels at only 4.2. A Spearman also costs only 70 resources while a Hoplite costs 120.
The Greeks, along with the Atlanteans have the only way to upgrade their titans.
Dionysus's Bacchanalia upgrade gives all myth units, including titans, 5% more hp. On a titan, that gives it a total of 7350 hp, as compared to the base 7000 hp.
Also, Hera's Monsterous Rage upgrade gives all myth units, including titans, 25% more attack of all types. On a titan, that gives it a total of 88 crush attack, as compared to the base 70 crush attack.