Anyway, when you start your revolution around the lamp/sun (always maintaining the Earth/ball at the angle you marked), you will see how the light hits the ball in different places as it moves around the center of light. Part of the revolution it's focused on the the north and the other, the south. When it hits both, those are what we call the vernal and autumnal equinoxes. It's a very helpful visual; I found it particularly so myself because I'm not great at spatial mental configurations. I remember an astronomy professor looking at me like I was an idiot once because I didn't get why we only ever see one side of the moon. Once I'd seen it drawn out however, it made perfect sense! Anyway, the above simple demonstration, is a fun way to demonstrate why there are seasons on the planet, and why there are places called, "lands of the midnight sun."
This is a great (and short) explanation as well from Universe Today:
(Fun fact: I've always loved the fact that Uranus basically revolves around the sun on its "side." Its axis is tilted at 97.8 degrees! It's like the giant gaseous bowling ball of our solar system!)