One definition of Barcamp is "Unconference".
But what is an unconference?
If you visit a Barcamp you will mention that nobody knows the topics of the sessions which will be held on this day.
Every session will be created and held by one of the members (=visitors).
The Barcamp Team tries to avoid the term "visitor", because everyone is part of the Barcamp. There are no visitors, only people who join a Barcamp.
The topics will be determined at the beginning of every Barcamp.
On the 2.+3. Barcamp Day the procedure continues.
You will see a wide variety of "Sub-Barcamps" with special topics like: