Can someone explain - why list initializers are used as variables in private access specifier. Why variable m becomes month m ?

Question

#include <iostream>
using namespace std;

class Birthday {
public:
Birthday(int m, int d, int y)
: month(m), day(d), year(y)
{ }
void printDate()
{
cout<<month<<"/"<<day <<"/"<<year<<endl;
}
private:
int month;
int day;
int year;
};

Answer 1

int m, int d, int y is reffered as month(m), day(d),year(y) during initialization and i cannot understand why? Is variable 'm' being assigned to month variable and so on?