I can't seem to find any easily accessible documentation on this, but it sounds like a container is basically an chroot jail: you copy over all the libraries and files into a subdirectory, chroot into it, and run. Am I right? And if so, what took people so long? Chroot has been around for quite a while.

The article sort of makes it sound like a lightweight version of containers would be putting everything in its own directory, rather than scattering everything in /usr/lib, /usr/bin, /usr/share, etc. Which is basically macOS' app bundles. I've never understood why other OSes didn't steal that idea. And while I hear a lot of griping about iOS and static libraries, basically what iOS is doing is creating a container, only since they call it an "application bundle" instead of "container" they get all this hate. But... Grandma Tillie (or whoever the user story for Linux on the Desktop back in the The Day was named) can actually figure out how to delete her Mac and iOS apps.

Seems like iOS is kind of containers writ large.