Saintpaulia is a genus comprising of approximately 20 species and subspecies, and many varietes. There are a fair few types including standard, trailers, miniatures, and chimeras (a basic way to put them into a category). Various species includes different sizes, flower colors and foliage types.
A grower needs to understand which type they have if they plan to propagate them - the procedure is different (for the Chimera). There are actually thousands of hybrids with various flower colors/forms and leaf types available.