Note that this set differs from the natural numbers by including 0. There are many different ways we can classify numbers. In fact,
many of the classifications are subsets of other classifications. For example, the set of natural numbers differ from the set of whole numbers by excluding 0. Therefore, the set of natural numbers is a subset of the set of whole numbers. The following table
gives depictions of how the classifications relate:

Natural Numbers 
Whole Numbers 
Integers 
Rationals 
Irrationals 
Examples 
1, 2, 3, 4,... 
0, 1, 2, 3, 4,... 
…, 3, 2, 1, 0, 1, 2, 3, ... 
1/4, 6/5, 0.125, 3.272727 
, 2.345678... 
What's new 

0 
Opposites of natural numbers 
Fractions, repeating and terminating
decimals 
nonterminating
decimals 
Together the rational and irrational numbers form a larger set of
numbers called the Real Numbers.
