I am not sure how to ask this question, but I need help in understanding the usage of :: when grabbing a member variable in a class? Rather than just typing that specific member variable instead? For...

I am not sure how to ask this question, but I need help in understanding the usage of :: when grabbing a member variable in a class? Rather than just typing that specific member variable instead?

For Example:

In Hpp file

#include

using namespace std;

class class_name{

void add_name(name);

string variable_name;

};

In CPP file:

void add_name(string name){

class_name::variable_name = name;

}