In 2005 Y Combinator held its first Demo Day. Eight companies showed off their products and sold their vision to an audience of about 15 investors. Today, accelerators and incubators around the world hold their own demo days, and in 2016 over 200 YC companies will describe their startups to an audience of hundreds. Creating an effective demo day presentation has become an important part of participating in YC, not just due to the importance of Demo Day, but because the very process of fashioning the presentation is valuable. Surprisingly, it can be the first time founders achieve clarity together and come to a shared understanding of their story.1

Source: A Guide to Demo Day Presentations · The Macro