Porter and Stout: What's the difference?

Great video from The Craft Beer Channel:

"This week Jonny and Brad answer the question that's puzzled beer geeks since the dawn of time – what's the difference between Porter and Stout? As well as tasting two classic examples, they dive into the history to work our the historical difference between Porter and Stout in the 1700s, 1800s and 1900s – and in doing dig up the origins of Guinness... and how that's different too. Stop saying different."