Explanation:
There are 4 kinds of real numbers:
Natural numbers - the counting numbers (1, 2, 3, ...)
Integers - positive and negative counting numbers, including 0 (..., -1, -2, 0, 1, 2, ...)
Rational numbers - can be written as a ratio of integers (1/2, -2/3, 4/1, etc.)
Irrational numbers - cannot be written as a ratio of integers (√2, π, e, etc.)
Natural numbers are positive integers. All natural numbers are integers, but not all integers are natural numbers.
Natural numbers are positive rational numbers with denominator of 1. All natural numbers are rational, but not all rational numbers are natural.
Natural numbers are not irrational numbers.