Final answer:
Natural numbers are positive integers that are greater than zero. They represent numbers that appear in nature and do not include zero and negative numbers.
Step-by-step explanation:
Numbers that appear in nature and do not include zero and negative numbers can be defined as natural numbers. Natural numbers are positive integers that are greater than zero. They are typically represented as {1, 2, 3, 4, 5,...}.
For example, the sequence {1, 2, 3, 4, 5,...} is an infinite set of natural numbers.