A long time ago in a place far away ... there were species bananas (Musa). These plants produce seeded fruits -- and by seeds I mean pea-sized seeds hard as a rock. You'll find many listed in the
Bananas Wiki. Each of the seeded species has a certain genotype: A, B, T, S -- briefly charted here:
INFO Genetic Names - Bananas Wiki. Over the millenia these interbred and in human times have been purposely cross-bred to produce hybrids: almost all of which are seedless bananas, and many of which are edible. So for example, an AAB was created by selected crossing of Musa acuminata x Musa acuminata x Musa balbisiana.
Banana "group" names refer to entire sets of bananas with the same geneology and similar
phenotype. Musa researchers formally call these "subgroup taxons". Some examples are: Pome, Mysore, Cavendish, Celat, Iholena, Maoli, Pisang Wawak, Pitogo. Just to make it more interesting, there are also individual bananas with the same name as the group they belong to.