Anyone know what this is? And how to use it?

That's algae and happens often due to overwatering. Light helps it to grow.

Root porn

Rockwall cubes that have been cut up?

Here is another pic

The green sod looking thing. Sorry should have been more specific. That’s from capulator Instagram and I’ve seen him show some beautiful looking roots using that.

know what, what is?

What are you talking about?