Most cultures, when they have earth gods and sky gods, think of the earth as female, and the sky as male. This makes sense in temperate areas, where the water that makes things grow comes down to the earth from the sky (as rain). Ancient Egyptians, and other desert-dwelling cultures often flip this around, because for them the life-giving water actually comes up from the ground and goes up into the sky (as moisture from rivers, desert oases, or dew). So in places where it doesn't rain very often, it's Father Earth and Mother Sky.
Geb's name in ancient Egyptian means "weak" or "lame." If it's written a different way, it means "goose," which is why Geb sometimes is depicted with a goose standing on his head (ow?). In several Egyptian creation myths, the "Great Cackler" is a giant goose that lays an egg (the sun/the god Ra). The song the Great Cackler sings while laying that egg creates everything else. Next time you see a Canada goose munching on someone's lawn, remember it's a symbol of creation, and leave it be. (Besides, everybody knows those things are vicious…)
Geb and Nut are part of the Heliopolitan creation myth from ancient Egypt. Heliopolis (or Iunu) was the capital city for a while, and always the biggest and most important temple city throughout Egyptian history, until the rise of Thebes and Amun's giant temple at Karnak far to the south. Geb and Nut form the middle of this creation story: First there was Atum, the creator. He created Shu (wind/air) and Tefnut (moisture/rain). Shu and Tefnut created Geb (earth) and Nut (sky). Geb and Nut had five children: Osiris (order) and Isis (life); Seth (confusion) and Nephthys (death); and Horus the Elder, whose Eyes were the sun and the moon.
Even though they have to be apart in order for life to exist, Geb and Nut have friends where they're at. Geb's an earth god, and hangs out with snakes. He's sometimes called Sa-Ta, or "son of the earth." Nut is a sky goddess, and hangs out with stars instead. These stars are called Akhu or "shining ones," and are supposed to be the souls of human ancestors. (Remember Simba looking at the stars in The Lion King? It's like that.)
The goddess Nut's name is pronounced to rhyme with "boot," and comes from ancient Egyptian words for "sky" or "container." She's a symbol of the night sky and its stars, as well as the vacuum of space. The French word for "night" is nuit. These words aren't related at all, even though they sound similar. That didn't stop a European fraternity called the Thelemites from calling Nut "Nuit," and writing poems about her. Ancient Egyptians liked puns. Maybe Nut doesn't mind? (But her name really is spelled Nut.)
Maybe you played a game called "snakes and ladders" as a child (either the official Chutes and Ladders version or another). Some people believe this game came from India, and there is a version that does come from there. But there are also ancient Egyptian references to snakes and ladders associated with Geb and Nut. Geb has snakes that grab evil spirits and punish them in his underground cave, and Nut owns a magic ladder that Osiris, and later any good person's soul, can borrow to climb to heaven.