A figure has symmetry if there is an isometry that maps the figure onto itself. If the isometry is the reflection of a plane figure, the figure has reflectional symmetry or line symmetry. If a figure has line symmetry, you could fold the figure along the line of symmetry and the two halves would match exactly.
I. Funny Face. Move the points on the left-hand side of the line of reflection to create a symmetrical funny face.
II. Symmetry Trace. Drag the green points to move the line of reflection. Use the blue point A to trace the figure on one side of the line of reflection (use Ctrl+F to clear the traces as needed).
III. Facial Symmetry. Drag the green points to move the line of reflection. Place the blue points on key facial features one side of the line of reflection to check for facial symmetry.