Bessel functions are a family of mathematical functions that arise in various problems involving cylindrical symmetry, such as heat conduction and wave propagation. They are named after the mathematician Friedrich Bessel, who studied these functions in the 19th century. Bessel functions are particularly useful in solving differential equations that describe physical phenomena in cylindrical coordinates. There are different types of Bessel functions, including Bessel functions of the first kind and Bessel functions of the second kind. These functions are defined for integer and non-integer orders and have applications in fields like engineering, physics, and signal processing. Their oscillatory nature makes them essential for modeling wave patterns and vibrations.