It provides closure under the binary operation of addition.
The set of positive integers contains 1 but not zero. Within the set of integers, there is the subset of positive integers, the subset of negative integers and the subset with a single element in it - zero. There are a zillion other sets that could be specified that meet the conditions set down in the question. The one cited is an easy one.
Integers
Negative integers, zero and the positive integers, together form the set of integers.
The set of numbers that consists of the positive numbers, the negative numbers, and zero are integers. There are no fractions in integers.
The set of integers is divided into three subsets. One is the positive integers. Another is the negative integers. The last subset has one element -- zero. In sum, integers are composed of the positive integers, the negative integers, and zero.
A set of integers contains all the whole numbers both positive and negative, including zero, from -∞ to +∞.
It means that the number is an integer, AND that it is not zero.
The set of Counting Numbers or Natural Numbersincludes positive integers but not negative integers or zero.The set is 1,2,3,4,5,6....and so on.
Whole numbers are integers greater than or equal to zero.
zero
These are the integers.
Extending the set of all integers to included rational numbers give closure under division by non-zero integers. This allows equations such as 2x = 3 to be solved.