One Definition Rule - Multiple definition of inline functions

I was reading ODR and as the rule says "In the entire program, an object or non-inline function cannot have more than one definition" and I tried the following...

file1.cpp

#include <iostream>
using namespace std;

inline int func1(void){ return 5; }
inline int func2(void){ return 6; }
inline int func3(void){ return 7; }
int sum(void);

int main(int argc, char *argv[])
{
    cout << func1() << endl;
    cout << func2() << endl;
    cout << func3() << endl;
    cout << sum() << endl;
    return 0;
}

file2.cpp

inline int func1(void) { return 5; }
inline int func2(void) { return 6; }
inline int func3(void) { return 7; }
int sum(void) { return func1() + func2() + func3(); }

It worked as the rule says. I can have multiple definition of inline functions.

• What is the difference between non-inline function linkage and inline function linkage?
• How the linker differentiate between these two?