1) they just ate every other 3rd party "secure" backup services lunch just like they did to the Hi-Res music industry.
2) details of what they backup securely, besides photos (which is top priority for me): iCloud Drive: Includes Pages, Keynote, and Numbers documents, PDFs, Safari downloads, or any other files manually or automatically saved to iCloud Drive.
3)BUT, perhaps the BIGGEST news here is that Apple is making a backup statement to what they've been saying for years and what they've recently gotten negative attention on: They don't want your data. They're not Goodle/FB/Amazon. They're giving you 2TB+ of space and you can encrypt it to the point that you'll lose your data and they don't care -- they don't want to mine your data, they don't want to know what you store on there, the don't care to scan your pictures with AI 20 different ways, they don't want to monetize it, etc, etc., just pay them money for their service and transactionally they give you only thing that you want in return -- reliable, secure, private service.
seriously, anyone at this point advocating for any other phone/os/service out there besides apple is really going out of their way to swim up river.