I understand they are a opportunity to find out more about a proposed course, it's structure, content etc
An opportunity to get a feel for the University and its surroundings.
What I'd like to know is does it form part of the admissions process? Are only limited numbers of candidates able to visit?
Why do people have to book? (Apart from wanting to know numbers) If you don't book can you still attend? Does not attending look bad for your application?