1. A new kind of asset
Investments have historically paid either a fixed return or a dividend that depends on how much profit a business makes. Prediction Perps introduce a new type of return: one that depends on what is happening in the world right now.
That return can follow the weather (temperature, rainfall), the league position of a sports team, the approval rating of a political party, or many other phenomena.
A position can be held for a day, a season or ten years. It can be a view on where something is heading, a way of backing a side, or a hedge against a phenomenon.
2. What today's markets can't give you
There are already ways to take a position on the weather or on a football team. These are all expiring positions, on specific questions with specific outcomes.