Should I apply for the Learning Disability Nursing course?

I've wanted to do it ever since I volunteered at a day care centre for adults with learning disabilities, however I had an interview today and my mind kept going blank and I feel like I don't know what a learning disability nurse really is?
Is there more to it then just what you see volunteering, if so what?
Im really confused though because I've read loads of things online and it's exactly what I think it is.

I'm worried that when I go to Uni I'll get asked a question in a lecture that everyone knows but me..
Did other people have this worry when starting a nursing course?

I'd feel so annoyed with myself if I gave up and didn't try though as I've dedicated so much time to volunteering (included other places including the day centre - so only been at day centre for around 10 days all together) around school time.