The Dab is the follow-up dance move to the Nae Nae. It basically involves leaning into your elbow to make it look like you're sneezing.
It originates from the Atlanta hip-hop scene and has been pretty widely adopted by American footballers too in recent months. 'Dabbing' also refers to a method of getting very high on butane hash oil, but you have the rest of the internet to teach you about that.
Anyway. Here's a pretty good example:probably over
Is the Dab his party trick now or something?
It's possible Gates is trying to show he's updated his shapes repertoire since the infamous Windows 95 launch party. But for our money, it's still the best thing on the internet: