What the Heck is the Semantic Web?

Egon Willighagen has been posting an interesting series of articles on the use of RDF in chemistry, the latest being this one. Being totally ignorant of what RDF is and why it's important, I challenged Egon to offer a simple explanation, preferably in the form of a video, graphic, or short paragraph.

In the meantime, I started doing my own digging. I found what I was looking for. But to put it in proper context, it's first important to understand what this Semantic Web thing really is.

Enjoy!

P.S. How hard could it be to come up with something similar to this video for explaining InChI and InChI Key?