These numbers are Arabic numbers, and Arabic numbers, which represent objects that cannot be divided, such as living animals, are called Natural Numbers. And to mark the value "none", the number 0 was defined.
So, natural numbers make up the representation of the number of undivided objects.
But with the use of subtractions, that is, when you had an animal, and sold it, you had one less animal, "this one less", was determined as an integer. Thus, Natural numbers, and Negative numbers, are the representation of the set of Whole Numbers.
In shops, they could sell themselves, half a cake, or half a kilo of flour. And that half kilo, or half cake, was not whole, and so it was not natural either. Thus, it was determined the set of Rational Numbers, thus generating the set of numbers that can be calculated parts of objects. Those fractions like half a pizza plus a quarter of a pizza. Or a pizza divided into 4 pieces, are determined as calculations of rational numbers.
But when we drive a car, and we want to see the distances covered, the numbers can be increased by very small values, such as the time measured in milliseconds. Those numbers that can be very small, or numbers like the one that determines a circle, which uses the value Pi, are determined as Real numbers. So, when we use physical, or chemical formulas, we usually use the Real Numbers.
We can see some examples, an apple number 1, belongs to Natural numbers. The person owes an apple, so -1 belongs to the Integer numbers. Half a pizza, so half, or 1 over 2 belongs to rational numbers. And a circle that measures 3 times pi meters, or 3 times pi belongs to the real numbers.
The Real numbers, we will see many times, so don't worry if you still don't understand.
