Like most hybrid dogs, there are four basic variations of the Cavapoo generational (formally known as "filial") hybrid: F1, F1B, F2 and F3. (Few breeders produce beyond the F3, and while there are breeders who claim that anything beyond F3 is formally considered a breed, it tends to be F7 that nearly all kennels and clubs accept as the first generation whose "hybrid vigor" is bred out enough for a hybrid dog to be formally considered a breed.)
The F1 Cavapoo — also known as the Cavoodle — comes from cross-breeding a Cavalier King Charles Spaniel with either a Toy or Miniature Poodle. This first generation hybrid, when crossbred with another F1 Cavapoo, produces an F2 Cavapoo; when two F2s are crossed, you get an F3 — and so on.
The variation within the variation, the F1B (and F2B, etc.), comes from cross-breeding a an F1 Cavapoo (or F2) with either a Cavalier King Charles Spaniel or a Poodle. (Just as with producing an F1 Cavapoo, the Poodle used is almost always either a Toy or Miniature.) Breeders tend to do this to either control the coat style or dog size.
There are a variety of coat styles that can occur when crossbreeding for Cavapoos, and while such coats range from merely wavy to big curls and may be slightly coarse or very silky, there is one rare coat color that is nevertheless more and more popular: the ruby (or mahogany) coat color. Most Cavapoos tend to have a two-color combination coat of white, brown, black and gray or a basically lighter, golden-colored coat; getting a Cavapoo pup whose coat will become a dark red, ruby or mahogany is difficult.
As with most hybrids that include a Poodle in the mix, there are three size variations with the Cavapoo: Toy, Miniature and Standard. The Toy Cavapoo (aka Toy Cavoodle) is 12-14 pounds and stands 10" to no higher than 12" tall. The Miniature Cavapoo (aka Miniature Cavoodle as well as the Mini Cavapoo or Mini Cavoodle) is in the middle but generally is the largest at 15 to 17 pounds and standing from 13" to 14" in height. Since people and breeders seek to breed down in size, there are far fewer of the largest Cavapoos, which weigh 18 or more pounds and stand 15" or higher. It should also be noted that as there is no formal recognition by kennels and clubs such as American Kennel Club (AKC) and the UK-based United Kennel Club (UKC), a lot of people (and breeders) tend to generalize the term Mini Cavapoo puppies when talking about Toy and Miniature Cavapoos.