Cannot understand the error msg: 'nonstatic member reference must be relative to specific object' [closed]

Answer 1

The error message clearly states that you are trying to access an object's member without an object: You need to distinguish classes and objects. A class defines how objects of that particular class look like, i.e., what data members and function members the objects support. You probably want to do something along the lines of

Employee worker;
worker.Info.ID = "ID";
std::cout << worker.Info.ID << '\n';

(assuming Info happens to be a data member of Employee whose type in turn has an ID data member.