Twin primes are pairs of prime numbers that have a difference of two. For example, the numbers 3 and 5 are twin primes, as are 11 and 13. Both numbers in each pair are only divisible by 1 and themselves, making them prime. The concept of twin primes is a part of number theory, a branch of mathematics that studies the properties of integers. The Twin Prime Conjecture suggests that there are infinitely many twin primes, but this has not yet been proven. Twin primes are an interesting area of research for mathematicians.