Natural Numbers: We know that Natural Numbers are counting numbers. We can represent Natural Numbers indefinitely to the right of 1 on the number line.
Whole Numbers: Whole Numbers are Natural Numbers including zero. We can represent Whole Numbers indefinitely to the right of Zero on the number line.
Integers: Integers are a collection of numbers consisting of all Natural Numbers, their negatives, and zero. We can represent Integers indefinitely on both sides of Zero on the number line
Rational Numbers: Rational number is a number that is expressed in the form , where  and  are Integers and .

In case of a Rational number, the denominator tells us the number of equal parts into which the first unit has been divided, while the numerator tells us ‘how many’ of these parts have been considered.
We can also represent Rational Numbers indefinitely on both sides of Zero on the number line
There are a finite number of Natural Numbers between any two Natural Numbers. Similarly there are a finite number of Whole numbers between any two Whole Numbers. But there are infinitely many Rational Numbers between any two Rational Numbers. The idea of mean helps us to find Rational Numbers between two Rational Numbers.