35 fully collapsible module positions??

Does this mean if they are not used they are removed or hidden?

I expected that if a module was not specified, it would be removed and a lower or side module(s) would move up to fill that space.

I would like user1 and advert1 - 4 not to add white space under the nav bar. Can I remove them if I am not using them?

Thanks for you help.

when and module position is empty (no modules in it) it does not appear.