Specification tree

When you click on the white line in the specification tree the whole model it turning into black colour, what does that mean? what is its significance?


I am not able to use the fracture of pad please tell me problem

![16555333951285710124883279021693|666x500](upload://5HBH65VH3eI5T9OYzkywG7fjRvF.jp

And not able to use the constraints defined in dialog box