A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. This means that a prime number can only be divided evenly by 1 and the number itself, making it unique in the realm of numbers. For example, the numbers 2, 3, 5, and 7 are all prime numbers. In contrast, a composite number is a natural number that has more than two positive divisors. For instance, the number 4 can be divided evenly by 1, 2, and 4, making it composite. Prime numbers play a crucial role in various fields, including cryptography and number theory, due to their fundamental properties.