Math- What does sum mean?

Sum, or summation, is just addition.

For example, the sum of 1 and 2 is 1 + 2 = 3. The term "sum" is generally used for large sets or series. For example, the sum of the first 100 natural numbers is 1 + 2 + 3 + ... + 100 = 495.

Sum is the total of 2 or more numbers as determined by the math process.

Mathematically it means the answer to an addition problem.