Real numbers are of two types: Decimal and Integers. The Integers have no decimal values like 0.33, 0.45; Decimals can be 0.23, 0.333… etc

Integers are of three types negative numbers like -1, -2 .. , zero and positive numbers like 1, 2, 3…

The negative numbers and zero are called non positive and zero and positive numbers are called non negative numbers.