What is a Sport?
A sport is a mutation produced vegetatively by a single plant that is different from the parent plant (no seeds involved). In hostas, this usually is a leaf color or pattern variation, although flower, scape, and even root differences on a new division would also be considered sports. Basically, your plain old green plant suddenly grows a leaf or sends out a new division with, for example, a white edge. Or your nice variegated plant suddenly produces an eye with solid green leaves.
A hybrid is a new variety produced, most often by seed, either from 2 different parent plants, or by self pollinating one plant that is itself a hybrid. Species plants breed true, but almost all of the hostas currently available commercially are hybrids, that is, the result of an earlier crossing of 2 different varieties. Therefore, when you cross 2 hybrids, you can get a wide range of different plants, none of which will be genetically identical to either parent plant.
Contributed by dhaven on the Hosta Forum