javascript syntax questioon

So lets say i have the following code:

 function c (f,i) {
        let x = i;
        if (f(x,i)){
            x--;
        }
        if (f(x,2)) {
            console.log(1);
        }
        else {
            console.log(2);
        }
    }

what exactly happens in the if statements, i dont understand the syntax behind it. f is no function, its a variable, so what happens here? does it equal to f * ( x * i) ? whats the operands behind this syntax. Thanks in advance