A Geometry Transformation is a figure that has moved or changed position, size, or orientation on a plane. Changing orientation means changing the direction it faces. Transformations can be rigid (same shape), or non-rigid (different shape).
A geometry figure is a reflection if it is flipped across a line of reflection. Think of when you look into the mirror and you see your reflection. Think of the mirror as the line of reflection and your image in the mirror as being as far from the mirror in the other direction as you are from the mirror.
An image before it is transformed (like yourself) is called the pre-image, and the final image is called the image (don’t ask me why!).