Volterra integral equations of the second kind are mathematical equations that involve an unknown function, which is defined by an integral equation. They typically take the form f(t) = g(t) + \int_a^t K(t, s) f(s) \, ds , where f(t) is the unknown function, g(t) is a known function, and K(t, s) is a kernel function that describes the relationship between the variables. These equations are named after the Italian mathematician Vito Volterra and are used in various fields, including physics, engineering, and biology. They can model systems where the current state depends on past states, making them useful for problems involving memory effects or time delays. Solving these equations often involves numerical methods or iterative techniques.