When I was new to the chicken world, I had silkies and bantams. I had heard the term "bantams" used so much, that I finally asked just what a bantam was. This is the response that I got, and maybe it will be helpful.
Chickens are broken down into 2 main Categories, those being Large Fowl (often mistakenly referred to as Standards), and Bantam.
So, Bantam is not a breed, it's a Category of all small breeds, most are miniatures, about 1/4 the size of their Large Fowl counterparts, but others are "True Bantams", such as Silkies, which have no Large Fowl counterpart. Other True Bantams breeds are: Booted, Belgian Bearded D'Uccles, Belgian Bearded D'Anvers, Rosecombs and Seramas. In other words they are found only as Bantams. All breeds, whether Large Fowl or Bantam have specific characteristics, or "Standards" as written in the Standard Manuals, size, weight, body shape are all specific to their breed. Colour and Patterns are specific to Variety.
The Classes of Large Fowl Chickens as described in the APA Standard of Perfection are: American, Asiatics, Continental, English, Games and AOSB (All Other Standard Breeds).
The Classes of Bantam Chickens as described in both the APA Standard of Perfection and the ABA Bantam Standard are: Feather Legged, Games, Single Comb Clean Legged, Rose Comb Clean Legged, and All Other Comb Clean Legged.
I know that I was confused, but that cleared up alot for me. Hope it helps others!!