According to the AKC, the Labrador Retriever has been America's favorite breed for the last 30 years. Once called the St John's Dog, these web-toed wonders were originally used to retrieve fish that escaped from nets and lines. This job then expanded to include retrieving waterfowl, which they are still doing to this day. Even though their name would suggest that they were originally developed in Labrador, Canada, Labs actually originated in Newfoundland, when fishermen crossed smaller water dogs with Newfies to create a smaller, more agile boat mate.
Labs have a thick, oily, double layer coat that protects them from the cold waters of their homeland. Their fluffy, muscular "otter" tails serve as rudders while they swim; so much so that working labs sometimes suffer from "swimmer's tail" where excessive use strains their tail muscles. A lab within their breed standard can weigh between 55 and 85lbs, though some may reach 100lbs due to obesity or a breeder focussing on bigger dogs. They come in 3 official colors - Yellow, Black, and Chocolate, although there are other controversial colors such as Silver, Charcoal, Champaign, White and "Red Fox" that may be found online. While White and Red labs are acceptable variations of Yellow and may be registered as such, the diluted colors - Silver, Charcoal, and Champagne - are often considered mixed breed dogs, as the dilute gene that produces them didn't pop up until the 50s (after 40 years of purebred dogs WITHOUT any diluted colors) and is suspected to have come from crossing with Weimaraners. The AKC does allow Silver labs - which is the diluted version of Chocolate - to register as Chocolate, but many show breeders frown on the practice.
If you're in the market for a Lab, you may hear people talking about "English Labs" vs "American Labs". Unless you're actually importing dogs from Great Britain and using the term to refer to their place of origin, there really is no breed difference between the two - a Lab is a Lab (unlike the American Cocker Spaniel vs the English Cocker Spaniel, which are recognized as two different breeds). These terms have actually (incorrectly) become a way to describe the difference between a bench-bred/show-bred lab (often called an English Lab) and the field bred/working variety (the American Lab). Bench-bred labs tend to be stockier, have a thicker build and a squarer head than their field-bred counterparts; working labs are generally slimmer, with longer legs and an insatiable appetite for fetching.
Due to their easy going and dependable personalities, Labs have become one of the preferred breeds for use in service dog work. They're also favorites for bomb or drug sniffing dogs. Labs can live about 12 years (give or take) and some of their primary health concerns are obesity, tendon/ligament strains and tears, hip dysplasia, arthritis, and cancer. Labs can be seen competing in almost every available dog sport, but do particularly well in Dock Diving, Competition Obedience, Nosework/Scent sports, Agility and Flyball.