Baby snails basically come from eggs. Note that all land snails would be deemed hermaphrodites, producing spermatozoa in addition to ova. However, certain aquatic snails, for instance Apple Snails, would be either male or female. However, the do mate.
Before reproduction, you will find that the majority snails perform some sort of ritual courtship prior to mating. This could last somewhere between say two to twelve hours. Snails actually inseminate each other in pairs so as to internally fertilize their ova. You will also find that any given brood may comprise of say up to 100 eggs.
Garden snails, for example, bury their eggs in whatever shallow topsoil is available, mostly while the weather is found to be warm and damp, by and large two to four inches down.