Piggy breeds

American:

This breed is also known as the English Cavy. The coat is smooth and short and lies flat to the body. This is the most popular and commonly seen breed. The Satin American is also recognized by the American Cavy Breeders Association (ACBA). Satin refers to the sheen of the coat; the satin breeds have very shiny, sleek coats. 

Abyssinian:

The Abyssinian has a very distinctive appearance. The coat is made up of multiple swirls of hair referred to as rosettes. Their hair is quite dense and coarse, and it radiates in circles from multiple points on the body to make up a series of whirls and ridges. For show purposes, Abyssinian must have a minimum of 8 rosettes, in a symmetrical pattern. These guinea pigs always look somewhat dishevelled.

The Satin Abyssinian is also recognized by the ACBA; again the satin simply means the coat has a deep shine.

Peruvian: 

The Peruvian coat is smooth and straight, and grows to several inches in length. The hair naturally parts down the center of the back, and also grows forward over the head.

The dense, soft coat of the Peruvian requires a great deal of grooming, and many owners of Peruvian guinea pigs end up trimming the hair to keep it manageable (if the guinea pig is to be shown, wraps can be used to keep the hair from getting tangled or soiled).

The ACBA also recognizes the Peruvian Satin (again, referring to the shiny quality of the coat).

Silkie:

The name says it all.:)

The Silkie is also known as the Sheltie, and has a very silky long coat. In contrast to the Peruvian, the Silkie's soft coat does not naturally part along the back, and grows backwards from the head.

A Silkie Satin (shiny coat) is also recognized by the ACBA.

Crested:

This is a short haired guinea pig with a single rosette (swirl) on the forehead. There are two types: one is the White Crested Guinea Pig (also called American Crested), where the crest is white in contrast with the rest of the coat (no other white on the body). In the "self" crested guinea pig (sometimes called English crested), the crest color is the same as the rest of the coat.

Teddy:

This short haired guinea pig is characterized by a short dense coat with bent (kinked) hair shafts that makes the coat stand on end, giving a very fuzzy appearance.

Texel:

This uncommon guinea pig has a very distinctive long curly coat.

Coronet:

The Coronet Guinea Pig is also long-haired, but has a single rosette ("coronet") in the center of the forehead. Like other long haired guinea pigs, Coronets need lots of grooming.

Other Varieties of Guinea Pigs

There are some other less often recognized varieties of guinea pigs. For example, other haired guinea pigs include the Merino (long curly hair with a crest on the head) and the Alpaca (long curly hair that grows forward over the head). In addition, there are many color variations which are also used to describe guinea pigs along with the breed.

There are also two kinds of hairless guinea pigs. The Baldwin Guinea Pig is totally hairless, although they can be born with some hair which is lost as the guinea pig matures. "Skinny Pigs" are hairless as well, but often not completely as there may be patches of hair on the face and paws as well as fine hair over other parts of the body.