This document discusses geometry transformations, specifically reflections and products of reflections. It defines reflections as isometries that flip a figure across a line of reflection, preserving collinearity, angle measures, and distance measures. Reflections have the property that a reflection followed by itself is the identity transformation. The document explains that translations, rotations, and glide reflections can all be expressed as products of two reflections. Translations are the composition of reflections across parallel lines, rotations are the composition of reflections across intersecting lines, and glide reflections combine a translation with a reflection across a parallel line.