These are those strange square black and white boxes. They're a two dimensional bar code, which can hold different kinds of information, but in this context they're being used for URLs.
There are various apps for mobile phones (there is even one for this conference) where you point your phone at the code, and your browser opens to the page the code references.
When you create a fundraising page on ActBlue we give tools for embedding in your web pages, and now we've extended that to generate a QR code. The code can even incorporate refcodes and preset amounts and recurring durations.
Download the code and use it in your print, and display media, giveaways, anything you can expect people to point a camera at.
If you have a code reader app on your phone (maybe this one for iOS), point it at this to see the demo: