What, exactly, is Amazon Web Services?

In the popular imagination, Amazon is a big huge store run by Jeff Bezos, a smiling man with a clean-shaven head who is, sometimes, the richest person in the world. You order and Amazon delivers.

Because it’s a big, huge store that wants to be bigger and huger, you can also stream TV shows and buy Amazon-branded personal gadgets and Amazon-branded home security devices. You can order groceries there, too. This is a version of the story Amazon has been telling about itself, to customers, since the very beginning, and one that has made it enormously successful.

But behind Amazon’s success is also a guy named Andy Jassy, whom most of the company’s customers had never heard of before Wednesday, when Bezos announced that he would succeed him as CEO.