What's the difference between Sia and Skynet? This is the point that confuses me most. I thought Sia is the low-level layer and Skynet is the high-level layer, but one of the comments says that Sia encrypts data and Skynet doesn't, so that makes no sense. Too many names that aren't clearly explained in a very obvious place is a plague that many otherwise cool projects suffer from.
Data on the Sia network is encrypted at a storage layer (as part of splitting it up to send it to hosts), but Skynet files are accessible to anyone who has its hash (portals, ISP, etc could see this info when you access the URL). The file contents are not encrypted by default because they're meant to be widely-accessible, but you can encrypt files on the client-side before sending the, to Skynet, which is what https://skysend.hns.siasky.net/ and some other projects do.