Any dog we may buy is as the result of some kind of breeding programme. This can be from a haphazard, even irresponsible mating perhaps of convenience, or as a result of an intelligent, well thought out plan.
Breeders will approach their breeding plan in different ways, experienced breeders are often dedicated to their own ways or methods. This is usually based on years of dedication to an approach that has worked for them. There is no short cut, and you cannot buy success.

Line breeding is the mating together of relatives, grandfather to granddaughter, half brother sister, aunt to nephew, or cousin-to-cousin could be considered line breeding. It is a less intensive form of inbreeding really. It is fair to say that a nicely line bred animal will usually have one common ancestor in the third generation appearing three times, (a common grandparent and or great grandparent), hopefully this will be an animal of quality. There will be a line running through the pedigree on both sides
The purpose of line breeding is to hopefully set certain characteristics in the progeny. You will see a ‘type’ develop. It is possible to look around the show ring or even at animals in the street and be able to guess fairly accurately who the ancestors are, or which kennel the dogs ancestors are from. It is again useful to know the animals in a pedigree. The advantages of line breeding then are, that you mostly know what you will get, and you can set certain characteristics that should be easier to replicate in future generations.
There is always a downside of course, and this can be when certain undesirable characteristics come to the surface. These can be very hard to breed out such as poor shoulders, and or tail set for example, and it might take a long time to do so – over generations.

This is the breeding together of closely related animals such as father to daughter, son to mother, or full brother to full sister.

When we speak of an out cross, we cross two completely unrelated lines of the same breed together. Although if we look back further than the fifth generation we are bound to find related animals occurring.
When we out cross we don’t know what we will get - either virtue or fault, though if one parent is closely bred (line bred), then we will have more idea. Breeders often use an out cross then come back closer to the line again to set any virtues they may have acquired. From an out cross we would expect the pups to all look different but there may be one that manages to combine the virtues of both parents!!
Each breed has dogs that were/are dominant sires who stamped their type on almost all bitches who visited them, some of the greats can be seen by studying pedigrees; the same names will crop up over and over again.
This has been taken from part of the work I did when at college. It is not intended to be exhaustive and is a guide only. It may not be reproduced in part or whole