Question regarding the syntax of someting related to macro in C++

#define minimum(mn, b) mn = min(b) 
#define maximum(mx, c) mx = max(c)
#define INF 10000000
#define toStr(a) #a
#define io(v) v.push_back()
#define FUNCTION(a,b) #

#include <iostream>
#include <vector>
using namespace std;

#if !defined toStr || !defined io || !defined FUNCTION || !defined INF
#error Missing preprocessor definitions
#endif 

FUNCTION(minimum, <)
FUNCTION(maximum, >)

int main(){
    int n; cin >> n;
    vector<int> v(n);
    foreach(v, i) {
        io(v)[i];
    }
    int mn = INF;
    int mx = -INF;
    foreach(v, i) {
        minimum(mn, v[i]);
        maximum(mx, v[i]);
    }
    int ans = mx - mn;
    cout << toStr(Result =) <<' '<< ans;
    return 0;

}

This is a sample question from a hackerrank question, so there would be some mistakes in it. I want to know what does the part

FUNCTION(minimum, <)
FUNCTION(maximum, >)

mean ? It doesn't look like a macro as it doesn't start with #define. The discussion forums too didn't have a good explanation about this part, just that it relates to the macro defined as #define minimum(mn, b) mn = min(b) and #define maximum(mx, c) mx = max(c). ' I want to know what's it called and some advice on good resource to read about it.

The title is poorly written as I have no clue what to refer to that doubtful part of code as.