Different snails reproduce differently, but most snails are "hermaphrodites." Being a hermaphrodite means that any given snail can be both male and female at the same time. This can make it a lot easier for snails to reproduce and quickly make a whole lot of snails! Some hermaphrodite snails do not need another snail to reproduce, but can make more snails all by themselves (this is called asexual reproduction). Other snails are hermaphrodites but still need another snail to reproduce (this is called sexual reproduction). There are also some snails that aren't hermaphrodites, but are either male or female, and must find a snail of the opposite sex to breed with.

Most of the big land snails you see wandering around southern California, called California garden snails, are actually from Europe and were intentionally introduced to California to eat as food (escargot is a dish that is made from prepared snails, and it's a French delicacy). These snails are hermaphrodites and need another snail to reproduce. I actually wrote an article about these snails and you can read it here:

Here's an excerpt from that article on the reproduction of these snails:
"California provides very good reproduction conditions for Helix aspersa. Like many snails, they are hermaphrodites, meaning each individual has both male and female reproductive organs, although they must still mate with one another to reproduce. In less ideal climates, they breed in the late spring or early summer, but in humid, tropical climates they can breed year-round, up to five times a year, and can even store extra sperm for up to a year in case they do not find another mate. The snails dig small holes in moist, soft dirt for a nest and lay around 80 eggs, buried about one inch deep. The eggs hatch a few weeks later, and the newborn snails take one to two years to mature, but can then repeat the process again, potentially parenting many more snails in their two-to-five year lifespan." Hope that helps!

Snails are really interesting! Most snails are considered to be hermaphrodites and have both male and female reproductive organs. Snails are able to reproduce when they are 1-year-old (they live to be about 5-7 years old but some as long as 25 years!) at which time they must find a snail partner to mate with. After mating, each snail will lay eggs either in the dirt (land snails) or behind a rock (marine snails). The eggs will hatch and a baby snail will be born after 2-4 weeks. While the baby grows and develops it stays in a nest near its parents for about 3 months before it is ready to go off into the world on its own. Did you know that snails will get really sick if they eat salt or sugar!! If you find a snail or have one as a pet make sure you only give it plants to eat. Thanks for the great question!

Snails reproduce with egg cells and sperm cells, like so many other animals, and most snails are either male or female. But some snails have both eggs and sperm in their bodies, so sometimes the sperm in the snail fertilize the eggs in the same snail. That doesn't usually seem to happen, though. Usually the sperm cells in the snail are already grown while the eggs are still young, so the sperm cells fertilize eggs in other snails. For snails in water, the snail often just sends the sperm cells into the water, and they swim to the eggs in other snails.

Snails reproduce the same way almost everything else does - they mate and lay eggs. Some snails are hermaphrodites, though (have both male and female sexual organs in the same individual), which means that two snails can fertilize each-other.