The LED Lights Flashing alternate because of the pulse given by the 555 Timer. When the 555 Timer turns OFF the current LED light will freeze and when it turns ON it turns off the current LED light and transfer to another. This cycle we can compare to a Christmas Light.
If you want to try. pressed the button once and it will light it up. and if you want it to pause try the next button hold it the lights will pause. ;)
