It is exactly what you have stated - any information on your application form could be asked about, to either get more details/clarification/explanation about.
In your application, you are only presenting certain aspects of your experience - this is often factual (e.g. your degree subject) but your interviewer could be far more interested in why you choose that degree subject rather than your experience of doing it. However, other interviewers might want to really understand what you liked/disliked about your degree - which again is less likely to be represented in an application.
Interviewers can also ask you about your opinions on current matters related to your experience too though. For instance, if your application referenced something about either learning about or utilising AI, I wouldn't be surprised if the interviewer asked you questions like what you thought about Chat GPT and your thoughts on how such AI technology could impact law firms.
Thank you very much for your answers @laurabeaumont @Jessica Booker. This was really helpful.Hey @futuretraineesolicitor!
I know this is targeted towards @Jessica Booker but thought I'd just add that I once had a VS interview at a firm (not the one I am ending up at) that started by quite literally reading and talking through my application. I don't think this applies to every firm but does depend on the interviewer. In my case, they asked general questions about my experiences and time at university. Half of my interview was spent on that! It is likely your application will be being within view during the interview and so very likely any work experience or information on your application could be asked about. I suppose it depends on how much freedom the interviewer has in what questions they ask - never hurts to be prepared for any question on your experiences!
Hope that insight helps - Laura