But first a bad joke: Two mushrooms were sitting in a dance club, no one wanted to dance with them. In fact not one of the girls there would speak to them. The one mushroom turns to the other and says, "I don't know why no one wants to party with us, we're such fun-guys."
The undersides of mushrooms ruffle with something called gills. Mushroom gills, when a mushroom is ripe, open to release thousands (millions?) of spores. Spore are the fungi equivalent of seeds.