Phone call about a potential job opportunity: how to ask questions?

Any tips would be appreciated!

A month ago someone I know helped pass my resume to a VP at FICC at a wall street firm, who said they might hire in the fall. Yesterday the VP emailed me to set up a brief call to discuss "potential job opportunity" today after 7 pm.

I don't even know if they actually have an opening, or what the potential opportunity is. What should I prepare to answer and what questions to ask not sounding stupid? I heard the VP works in fixed income, but not so sure.

PS: one of the best firms on the street so would really love the opportunity to get an onsite.

Thanks