It has 0 lines of symmetry because we cannot reflect any portion of itself over the line to land on another portion. For example, we cannot draw a vertical line through the center and reflect the right half over to the left side. The arrow doesn't match or line up properly.
It does however have rotational symmetry. The angle of rotation is 360/3 = 120 degrees. We can rotate the figure 120 degrees, either clockwise or counterclockwise, and the resulting figure will be 100% identical to the original figure. In short: after the rotation, no change has been made. This is because the arrows are effectively going in a circle. Applying a rotation to a circle does not change the circle overall.