How to create green coffee? On the weekend, I've visited the vienna coffee festival. I've tasted "green coffee" there. Its taste and look was similar to green tea.

Is it a tea, created from the leaves of the coffee?

I tried to search it on google, but I've found "green coffee capsule" advertisements only.
What I have seen online suggests that it is what one would think of as severely under roasted (by coffee standards) coffee.  The flavor profile is very different than traditionally roasted coffee and much closer to tea with a lot of bitterness from compounds that are generally roasted off.

Sweet Maria's Green Coffee Cupping