Chebyshev refers to a family of mathematical concepts and tools developed by the Russian mathematician Pafnuty Chebyshev. He is best known for his work in approximation theory, number theory, and probability. Chebyshev polynomials, for example, are a sequence of orthogonal polynomials that are widely used in numerical analysis and approximation. In addition to polynomials, Chebyshev's work includes the Chebyshev inequality, which provides a way to estimate the probability of a random variable deviating from its mean. This inequality is fundamental in statistics and helps in understanding the distribution of data, making it a valuable tool in various fields, including finance and engineering.