Depending on the professor, will go through rounds of interviews. You will talk to their group/team. They will ask about your previous experiences, and also ask you what's the reason why you want to be a PhD, and your future direction.
I reached out to individual principal investigators across departments and asked if they had an opening I could interview for. I recommend reading their papers before meeting them. I had a professor ask me to submit a written summary of some of their papers.
Talked with professor. Nothing much. Had discussion on science and personal related items. Talked about potential projects. I was asked about strengths and weaknessess. I think interview here PI is much more improtant sadfasdf