
Line-breeding is a stage less closely related than in-breeding. It involves using dogs and bitches with common ancestors in their pedigrees three or four generations back. It is a system that allows a breeder to evolve the type of dog they admire, but will "fix" characteristics comparatively slowly.
Out-crossing uses animals from totally different families. The puppies will be very varied in type, with the occasional super animal, but most of them will be fairly nondescript. The careful introduction of an outcross into a line is used to bring in another desired quality,but shouldn't be repeated consistently.
Basically, the more distantly related the parents, the more varied will be the quality of the puppies. The average breeder is best advised to play safe and line-breed, and not risk an outcross. It can take many generations to correct a carelessly introduced fault.
Hope this helps.
:)