Composite number is a number that could be formed by multiplying two or more whole numbers greater than a unit. Example: 4, 6, 9..
Composite numbers are those numbers which have more than two factors and can be divided by more than just 1 and themselves. Composite numbers are so called because they are composed of more than two factors and can be even or odd.
Let us find factors of 12 and 15. The number 12 has factors 4 and 3. 4 could be further factorized into 2 x 2 so, basically 12 has factors 2 x 2 x 3, while 15 has 5 and 3 as factors and so they are considered as composite numbers.