Explain AWS Like I'm Five

Total world domination by controlling all the servers.

:-P

Amazon is a big-ass engineering company and they have built and/or tuned a lot of computers. As part of their service, they sell computer time to anybody who wants to use it to host their stuff. At first it was pretty basic when "cloud" itself was a pretty innovative idea. But as they have grown, they have released a lot of specialized services. So whether you need to store things, serve data, or general computation, AWS serves as a pretty nice menu.

AWS was early to the party but Google, Microsoft, and others have similar offerings, and the companies are always competing on new products and pricing. Boutique operations which specialize in usability, simplicity, or serve a niche, fill out the rest of the market.