A Reflection Group is a mathematical concept in the field of group theory, which studies symmetries. Specifically, it consists of a set of transformations that can be represented as reflections across hyperplanes in a vector space. These groups help in understanding the symmetrical properties of geometric objects and can be classified based on their dimensions and the number of reflections involved. Reflection groups are closely related to other mathematical structures, such as Coxeter Groups and Root Systems. They play a significant role in various areas of mathematics, including algebra, geometry, and even theoretical physics, where they help describe symmetries in physical systems.