This is an RPG heavily slanted towards story telling as opposed to simulation. So slanted that it actually does not require a game master to run things. It is like a game version of a round robin story or the old writers' game of the "exquisite corpse"
At the start, the players create the ground rules and background, then the story begins.
Each player starts with twenty-five coins (pennies or the like). Players spend coins to establish elements of the game. These include contexts ("this is a Conan the Barbarian sword n' sorcery"), setting ("on ancient Atlantis"), social rules ("no Schwarzenegger quotes"), characters, things, places, and, later in play, events. Establishing any fact costs a coin. Later, a player who has an issue with an established item may erase it by spending as many coins as the number of facts inherent in the item. Erase items are ignored for the rest of the game.
Players get back coins at the start of each scene, and as the result of resolving a Complication.
Characters or other "volitional" items are controlled by their creator, though their controller may be changed by spending a coin. If two groups of characters under different controllers come into conflict, a Complication occurs.
Complications have complex rules, but basically everybody involved brings relevant items to the resolution (and creates new items just for this Complication) and this determines how many dice each side can roll. High roller wins, but must spend lots of coins. Coins are spent and some change hands.
So this mechanism adds formal rules to a round robin story thus creating an RPG. If you are curious about how this works in practice, there are Example of Play to read.
You can find out more by reading the reviews.
It is even possible to use Universalis as rules for large army miniatures wargaming.
There is a variant where the rules for Universalis are merged with the rules for The Pool to create an interesting hybrid called UniPool.