Let us look at Square. We rotate the square by 90 degrees and observe that the figure looks exactly same as it was in the original Position. Further we again give a movement of 90 degree to the new position of the square and find that it again appears symmetrical to the original position. Thus we come to the conclusion, that after the rotation of 90 degrees, 180 degrees, 270 degrees and 360 degree rotation, the square appears in rotational symmetry. This position of symmetry is found 4 times while one complete rotation of the Circle i.e. 360 degree rotation is given to the figure. Thus, we say that, square has rotational order 4 and the degree of rotation is 90 degrees.
We further say that, if the figure matches its original shape for a number of times, while it is being turned about a point called the center of rotation, then we call that figure is having a rotational symmetry. We also define the rotational symmetry as number of positions any figure can be rotated to, such that there is no change in its original looks, and then we call it the order of rotational symmetry of the given figure.
Hence in the rotational symmetry, we say that the figure can be rotated by some angle but still looks as original shape of figure. At such a position, we say that figure is in the rotational symmetry.