How to select objects

There is this option in many mapping tools that's called 'Require bookmarks', what does this mean?

Not checking 'Require bookmarks' will make the program target ALL the objects in the map.

After checking 'Require bookmarks' the program will only do work on the marked objects. You mark the objects by putting bookmarks on them. The bookmark may be anywhere in the object's temporal range, so for example a bookmark may be on the sliderhead, sliderbody or sliderend and the slider will be marked.