There are numbers, having exactly two factors 1 and the number itself. Such number are 2, 3, 5, 7, 11, and so on. These numbers are prime numbers.
The numbers other than 1 whose only factors are 1 and the number itself are called Prime numbers.
There are numbers having more than two factors like 4, 6, 8, 9, 10 and so on. These numbers are composite numbers.
Numbers having more than two factors are called Composite numbers.