IBC or COI% - Inbreeding coefficient is a term that is becoming much more popular these days. In layman terms: It is an estimate in percentage rate of related ancestors in a dogs pedigree. Meaning the % of common genes from related ancestors.
Inbreeding is a term normally used for breeding close relatives like Father to daughter, sister to brother etc. The term linebreeding is used when breeding dogs who are related further out, cousins, aunts and uncles. This is done to produce desired traits "cookie cutter" dogs so to speak.
Inbreeding and linebreeding is a way of increasing the likelihood of diplicating a desired trait but it can also have dire results. The term inbreeding depression is caused by increasing the number of similar genes which leads to undesirable recessive traits manifesting themselves in a litter. One common effect is low birthrate.
As most breeds started out with a small gene pool it can be difficult to find dogs that have no related ancestors several generations back. But some breeders after doing extensive research are opting for: outcrossing; which is when two unrelated dogs are bred together in hopes of adding "new blood" or vigor to a line of dogs. Many breeders are outcrossing internationally now with the available frozen semen shipping and insemination practice.
There is so much to know about breeding animals correctly. Not a casual undertaking by any stretch of the imagination. Making it very difficult for the casual pet owner to even know how to go about finding a good and ethical breeder these days. More on that later.