There are plenty of breeders on the forum who can answer this one, but my understanding is that an F1 labradoodle is the product of a Labrador retriever and a poodle, preferably from parents who check out clear for hip and eye problems and are of excellent health and temperament. The F1 offspring tend to have a wide variety of coats and configurations. An F1B labradoodle is usually the product of a poodle bred to at least an F1 labradoodle. This cross results in a pup with a more predictable coat and they're more likely to be nonallergenic and nonshedding.
There is no such thing as a purebred or pedigreed labradoodle because labradoodles aren't an accepted breed currently.