Not chosen for the initial position I applied for but asked to meet up at a coffee shop for another position

I applied for a position that I was not fully qualified for but felt like a good fit based on my experience and ability to learn quickly. The interview seemed to go well. After the technical questions were answered the hiring team kept talking about how great the benefits are, that this was the best place they had ever worked, and it ended with us all talking and showing pictures of our pets.

Two weeks later, they let me know that the position I initially applied for had been filled but that I had made a positive impression. The hiring manager asked to meet for coffee and discuss another position that had opened up.

I accepted the invite but cannot find a job listing or description for this role and am not sure how to prepare for what I’m guessing is a second interview. I have a general idea based on the position title and nature of the company but I still feel like I’m scrambling.

Is it normal to be asked to discuss a position when the interviewee has little to no knowledge to prepare,