We know that a rigid transformations preserves side-lengths and angle measures of a figure in such a way that the figure doesn't shrink or get enlarger. It creates congruent figures.
The three main rigid transformations are:
a) reflections, b) rotations, c) translations
On the other hand a dilation changes the size of the image when the scale factor is not equal to 1. It does not produces congruent images.
