The evolution in time of isolated subpopulations assigned to a same breed is the origin of the natural diversity that arises in any breed animal enriching it. The Iberian Pig breed has not been unaware of this process, accumulating throughout the centuries a great intra-breed heterogeneity that is reflected by a high FST value (0.19) among the subpopulations analyzed. In the present study we will undertake the assessment of the internal genetic diversity of the Iberian Pig breed with special attention to the four main strains (Negro Lampiño, Entrepelado, Retinto and Torbiscal), without forgetting others strains and lines that integrate Iberian Pig Breed. To that purpose, we based on different characterization studies of the strains and lines of the Iberian Pig breed. We emphasize not only their genetic differences but also the differences among their meat products for fresh consumption (tenderloin) by strain, in which Negro Lampiño shows the higher percentages of protein, water-holding capacity (ARC) and intramuscular fat infiltration (23.74, 17.06 and 5.28, respectively), defining a differentiated quality. Finally, we expose a classification to explain the population structure of the Iberian Pig Breed.