Each attendee will get $1M to "invest" in companies pitching.
The top two companies receiving the most "investment" will get $50K and $25K actual investments.
Another $15K will go to a completely random company (The Dartboard Prize).
Finally, $5,000 in actual money will go to the attendee with the best "portfolio", $3,000 to second place, and $2,000 to the attendee with the "worst" portfolio (The Contrarian Prize).
When you decide to invest in a company you meet at Demo Day, they will follow the same Handshake Protocol that Y Combinator uses.
In a nutshell, this just means that once you shake hands (or fist bump) on a deal ("$X via YC SAFE at a $Y valuation cap), the company will send you a quick email confirming it.
Just reply yes to that email, and the deal is sealed. (Actually signing the SAFE and sending the funds can then happen over the next few weeks.)