Chebyshev functions are mathematical functions that help in understanding the distribution of prime numbers. They are denoted as θ(n) and ψ(n), where θ(n) counts the prime numbers less than or equal to n, and ψ(n) counts the prime powers less than or equal to n. These functions are named after the Russian mathematician Pafnuty Chebyshev. The significance of Chebyshev functions lies in their connection to the Prime Number Theorem, which describes how primes become less frequent as numbers increase. They provide important estimates for the number of primes in a given range, aiding in number theory and related fields.