What does :: mean and do?

Answer 1

it just says the programm, that the following funktion is in the class that comes before, so in this example:

Class::func()

the func() is the funktion/constructor (in this example it's a funktion)
Class is the Class in wich the function/constructor stands ;)

Answer 2

scope(::)it is used to call the function outside the class

Answer 3

:: is called the scope resolution operator and is used for the purpose of inheritance in c++

Answer 4

This Scope resolution operator