A simple answer about hybridization sums it up. The "hybrids" you're talking about is a vague term. Either cross-breeds within species, or cross-breeds between species is the more concise terminology.

But I'm never satisfied with short answers. :^)

The thing with cross-breeds between species is that they are almost always likely to never live past conception as long, as the species are not in the same taxonomic family. If they are in the same taxonomic family, then it becomes varied with two outcomes: Infertile/sterile off-spring, or in the rare occasion they breed fertile/non-sterile off-spring (this is something that only happens when species are close enough in evolutionary divergence to have similarities in DNA to their predecessor/progenitor species).

Cross-breeding within species is something that we see all the time with dogs, humans, domesticated cats, etc...because they're all still homo-sapien, Felis catus, Canis lupus familiaris, etc etc...