these terms generally mean main food source, and just imply what they generally are better at digesting like, a horse can eat grass and digest it, so like a deer or a horse can eat meat it just could not live out of a meat diet as their bodies are more prepared for plant matter digestion, while ommnivores generally mean they could live just eating one of the two, like a bear, that would get a bit thinner with a only plant diet as there is less easy fat but would be alright if he can find enough of it