You begin as the ruler of a single planet, perhaps a new species reaching the stars, perhaps refugees or dissidents from an older empire settling a new world.
You begin with a small army and a small reserve of cash and food. It is your responsibility as leader of your empire to ensure the health and safety of your citizens. You will find that this demands growth, and you must figure out how to achieve growth without destroying the economy. Or antagonizing your neighbors.
You are not alone, either. Before you or any other intelligent life forms arrived, the galaxy was populated by strange aliens known as Gatharians. Reports vary as to whether they are actually intelligent or just kind of half ok at pretending. They are clearly none too bright at times. What other species would have an "East-West" section of their empire to go along with the "Northeast"?
Additionally you have competition. Intelligent spacefaring life has arisen on other worlds besides your own, and in fact new empires will in general tend to appear on a fairly regular basis. Some of these empires may be hostile. In some cases you may decide you wish to annex or destroy another empire.
Most of the lifeforms you will encounter will be intelligent. Now and then you'll discover a semi-intelligent or even nonintelligent species that somehow manages spaceflight and a sufficient degree of organization to be considered an empire. You may also discover intelligent species that you cannot communicate with no matter how hard you try. Such are the exceptions rather than the rule, however.
Consequently it will usually be to your advantage to negotiate rather than fight. The game comes with a complete system for handling communication with other empires. Utilize it to its fullest extent. Even if just to announce the fact that you are about to begin a campaign to annihilate somebody. The game's chief interest is in political roleplaying and negotiation. As a wargame it falls rather short.
Espionage and covert operations are a fact of life in the galaxy. Many a war has been started when a terrorist group got traced to its empire of origin. On the other hand, good intelligence can prevent military disasters, and sabotaging your enemies' armed forces is a lot easier than defeating them in battle. Furthermore, why waste effort developing secret weapons or money acquiring them on the black market when you can swipe ones that might otherwise be used against you?
The game supports many additional features beyond those outlined here. Some you will discover quickly after playing. Some you might never notice after playing for months, until some particular combination of circumstances arises. There isn't room here to go over everything, and besides, that would be telling, wouldn't it?
Hosting a PGE game requires a Unix or Unix-like system, a few megs of disk space, someone to serve as game administrator, and at least ten committed players who will keep up with the game and play regularly. More players are better, up to at least 25-30 or so. The game has never been playtested with more than that. To host a game, you need to download the source code.
Playing a PGE game requires getting access to a game that someone else is hosting, and a Unix or Unix-like system to run the client program on. You'll need to download the client source code and compile it. The client-to-server protocol is public; the documentation comes with the client source.
As far as I know, no games are currently in progress. The server also hasn't been updated since 2000. Sometime I hope to bring PGE back as a web application.