Think about your own body. If you drew a line down the center of your body from the top of your head to the bottom of your feet, your body on one side of the line would be almost identical to the part on the other side of the line. If they were exactly identical, we'd call the line a line of symmetry. You can think of a line of symmetry as a fold line. If you fold a figure on the line of symmetry, the figure will fold right in half, with both sides right on top of each other.
Some figures have more than just one line of symmetry, and some have none.
Consider the 3 colored designs below. First investigate the symmetry including the colors inside. In other words, red would have to fold onto red. Check your answers. Check your answers.