Numbers are used to quantify and measure things. They can be classified into various types such as whole numbers, integers, rational numbers, and irrational numbers.
Whole numbers are the numbers 0, 1, 2, 3, 4, ... and so on. They do not include negative numbers or fractions.
Integers are the set of whole numbers and their negative counterparts, along with zero. They are represented as ..., -3, -2, -1, 0, 1, 2, 3, ...
Rational numbers are numbers that can be expressed as a ratio of two integers, where the denominator is not zero. This includes fractions and terminating or repeating decimals.
Irrational numbers cannot be expressed as a simple fraction and their decimal representation goes on forever without repeating. Examples include the square root of 2 and pi.
Real numbers include all rational and irrational numbers. They can be represented on the number line.
Complex numbers are numbers of the form a + bi, where a and b are real numbers and i is the imaginary unit (i.e., the square root of -1).