Answer:
The "difference".
Explanation:
In the equation 7-5=2, 2 is the "difference" between those numbers. Be careful when calling it a product though, because a product is the result of a multiplication equation!
*Bonus nonsense: The first number (7 here) is called the minuend, the second number (5 here) is called the subtrahend, and yes, I totally looked that bit up.