Composite number is a number, that is not prime.
For example, 6 is composite number because its has other factors except 1 and 6, namely, 2 and 3.
By convention 1 is not composite.
This means that 1 is neither prime, nor composite.
Example 1. Determine whether 27 is composite.
Composite because 27 is divisible by 3, so 3 is factor of 27.
Example 2. Determine whether 31 is composite.
It is prime number (not composite) because it has only two factors: 1 and 31.
Now, practice a bit.
Exercise 1. Determine whether 37 is composite.
Answer: not composite (prime).
Exercise 2. Determine whether 121 is prime.
Answer: composite. Hint: 11 is factor of 121.