The document discusses transformations in geometry. It defines a geometric transformation as a bijective mapping between two geometries that maps points to points and lines to lines. Reflections, rotations, and translations are provided as examples of geometric transformations in Euclidean plane geometry. It is shown that reflections, rotations, and translations are isometries that preserve distance, angle measure, and area. The composition of transformations is also discussed, and it is shown that the composition of isometries is again an isometry.