Why do we need 2 constructors?

Answer 1

~swim~
Does that explanation answer this..?
#include <iostream>
using namespace std;

class MyClass {
public:
int var;
MyClass() { }
MyClass(int a)
: var(a) { }

MyClass operator+(MyClass &obj) {
MyClass res;
res.var= this->var+obj.var;
return res;
}
};

int main() {
MyClass obj1(12), obj2(55);
MyClass res = obj1+obj2;

cout << res.var;
}