Shouldn't take long! Keltham would have needed to explain those to explain Governance anyways!
A prediction market is when lots of people bet on something observable, instead of it being a bet between just two people. Let's say that a prediction token pays out 1 gold (100 copper) if it rains at any time tomorrow, or pays out 0 copper otherwise. Then Alis can say 'I'll sell Rain Tomorrow for 60 gold' if she thinks the probability of rain tomorrow is noticeably under 60%, and Bahb can wander up and say 'Sure I'll buy at 60' if he thinks the probability of rain tomorrow is noticeably over 60%; and then if some clouds show up at evening today, Karal says, 'I'll buy at 75', and Bahb thinks that 75 sounds around right to him, so he sells his shares to Karal and pockets a 15-copper profit per share.
Blah blah market-makers hang around and sell or buy based on technical market trends about what the public information looks like, instead of on the basis of having private information, so people can buy into the prediction markets at only very slight premiums, even if nobody else has private information right then.
Blah blah you can subsidize a market by saying you're willing to buy or sell at your starting estimate of 60% or whatever, and then anybody who disagrees with you about that in either direction will wander up and buy or sell from you.
Blah blah this is a very simple automatic market-making algorithm if somebody wants to subsidize a market continuously and isn't worried about losing a bunch of copper whenever it rains out.
Blah blah you can ask a bunch of separate questions for 'what's the chance X happens if we do this, or this, or this'. You only end up doing one thing Y; the market on 'does X happen if we do Y?' pays out 1 gold if X happens; all other markets are negated and everybody gets back their original investment (as it was kept in some standard store of value like equity in a huge basket of well-known corporations).
Civilization aggregates votes into Delegates then Electors then Representatives then Legislators. Legislators negotiate among themselves about what Civilization wants to have happen, and debate arguments from Very Serious People about which observables to measure to get at unobservable outcomes. The actual step of predicting which policies yield which observables is done by a policy prediction-market, and then, usually, the Legislators do whatever's predicted with the highest probability to lead to observables that seem like they should strongly tie to a good actual outcome there. Unless the 'best' policy according to the market looks like it'll have bad effects that nobody has figured out how to predict observable correlates about. Which, like does ever happen, but causes a lot of Very Serious People to start shrieking angrily at the Legislators and each other.
A few years or sometimes decades later, the observables come in, and the prediction market for the action actually taken pays out.
Once they get to the point where anybody besides Keltham knows anything about Prestidigitation-chemistry and spellsilver mining, and they've got more experiments to consider trying than they have resources to try, Project Lawful will obviously set up and subsidize an internal prediction market on which chemistry experiments will pan out.