Material Design Components Site

Today I was Googling for "material design components" I ended up at this site:

https://material.io/components/

As I remember, I've never seen it before.

In the Android section there are instruction to use the components and ok, it seems to be the well-known Android Design Support Library:

But what intrigues me is that there are components there that are not in the design library, such as:

Back Layer Layout, Material Card and Material Button.

The docs for these classes seems to be not ready yet and the links points to nowhere, like: material button doc.

There is something in the github site.

Sorry for ignorance, but what is the purpose of this site? Is it something future or something left behind?

The Android Design Support Library was the precursor of the Material Design Components. As of the Support Library 28.0.0-alpha1 release, the Design Library now contains all of the new components introduced in the Material Design Components:

We’ve introduced a new application theme, Theme.MaterialComponents, with new attributes and updated styles for components.

We’ve added the following components:

• BottomAppBar
• Chip
• ChipGroup
• MaterialButton
• MaterialCardView

While the 28.0.0-alpha1 release does contain all of the new classes, the documentation on developer.android.com does not yet contain the updates from the Design Library (keeping the docs effectively on what was publically available previously), but they are definitely there if you use that dependency.