Can anyone explain what this actually is? I get that it's apparently an exciting new project, but what actually is it? A framework? A programming library? A data specification? I honestly can't tell.

They refer to "applications built using the Solid stack" at one point, which implies that it's an application platform. But elsewhere they talk about how it's "a proposed set of conventions and tools", which implies that it's an interchange data format.

What am I missing?