A congruence transformation is a type of geometric transformation that preserves the shape and size of a figure. This means that when a shape undergoes a congruence transformation, it can be moved, rotated, or reflected without changing its dimensions or angles. Common examples include translations, rotations, and reflections. These transformations are essential in geometry as they help in understanding the properties of shapes and their relationships. For instance, when two shapes are congruent, they can be perfectly superimposed on one another. This concept is often used in various fields, including mathematics, engineering, and computer graphics.