This is a relatively small family of less than 20 species, but there are hundreds of cultivars. They are bulbs that produce white flowers in the late winter and early spring.
There are some species that start even earlier, G. reginae-olgae, for example starts flowering in late October, with G. caucasica var. hiemalis a month later. If snowdrops flowered in the summer, they probably would not be of such interest and there certainly would not be so many cultivars, but in the depth of winter they are particularly welcome and any little variant is seized upon.
You have to look closely for the variations, which often involve such minute detail as the shape of the green markings on the inner petal. Snowdrops are best bought while they are growing and not as dried bulbs. Plant out after flowering while the leaves are still green. They can also be moved or split after flowering. Clumps should be regularly split to keep them flowering well.
They are generally best suited to lightly shaded positions. They do not like too rich a soil; a woodland soil that does not dry out completely is ideal. Increase by division of the bulbs.