Manifold Markets is a play money prediction market with user-created questions. The play money can be redeemed as a charitable donation.
A video tutorial is also available.
Mana (M$) is the currency of Manifold. Users start with M$500 for free. M$ can be redeemed as a charitable donation at M$100:$1 or purchased at the same exchange rate
Markets are the unit of prediction on Manifold. Creating a market costs M$50, which is then used as a liquidity pool to allow users to trade on the market.
Most markets are yes/no (e.g. 'Will a nuclear weapon be detonated in 2022?'). Users buy 'shares' at a price determined by the current bet (the lower the probability assigned to your outcome when you bet, the cheaper the shares), which each resolve to M$1 if you're correct, or M$0 if you're wrong.
Note that you can embed Manifold Markets in foum posts and wiki entries!
Here's an example market; we can buy shares for yes or no with the purple arrows:
Below, we've spent M$10 in favour. Because the market is at 20%, this buys us 53 YES shares. If the market resolves yes, we'll net back M$53 for our M$10 investment:
We can also click on the title to see more information, make larger bets, and sell our shares (at their current price as determined by the market's aggregate bet):