What exactly is inbreeding in dogs?

Inbreeding is a method of breeding in which male and female dogs that are very closely related by blood are mated to produce offspring. That is, matings between father and daughter, mother and son, and brother and sister. From the standpoint of moral norms and scientific principles, humans consider inbreeding absolutely harmful to the evolution of the breed, but from the perspective of dog breeding, inbreeding can reduce genetic variation and preserve the original superior qualities. However, inbreeding may produce particularly outstanding puppies, and it may also produce puppies that are weak in constitution, deformed, intellectually disabled, and incapable of reproducing. From the standpoint of medicine and eugenics, the method of inbreeding should not be encouraged or widely adopted. But for certain needs, inbreeding is indeed a relatively good means of fixing a dog's genes.