The document discusses properties of addition and subtraction of integers. It states that integers are closed under addition and subtraction, meaning the sum or difference of two integers is always an integer. For example, 2 + 3 = 5. It also explains that addition is commutative for integers, so changing the order of numbers being added does not change the result. However, subtraction is not commutative, so changing the order of numbers being subtracted can change the result. For example, 23 - (-30) = 53, but (-30) - 23 = -53.