Moon-chan Kissing Earth-chan

Alright listen up, nimrod. This joke is for you, because you're clearly struggling. It's making fun of the whole "-chan" thing people online do with countries and celestial bodies. Moon-chan and Earth-chan are personifications of the moon and Earth. And the joke is that the moon hits the Earth, which is supposed to be this romantic moment. Bet you didn't know that the moon causes tides on Earth, huh? Also, Earth is not flat like your brain.