The Inverse Function Theorem is a fundamental result in calculus that provides conditions under which a function has a locally defined inverse. Specifically, if a function is continuously differentiable and its derivative is non-zero at a point, then near that point, the function is invertible. This means that you can find a unique output for each input in a small neighborhood around that point. This theorem is particularly useful in multivariable calculus, where it helps in understanding the behavior of functions of several variables. It ensures that if certain conditions are met, the inverse function will also be continuously differentiable, allowing for further analysis and applications in areas like optimization and differential equations.