Is carrion herbivores?

Seals are carnivorous, that means that they eat meat. seals are carnivores because they eat fish and they only eat meat because if a seal ate plants only it would be a herbivore but if it only ate...

A raccoon is an omnivore because it could eat fish and it could eat berries.

No. Herbivores eat only plants which is why they are called herbivores. A creature that eats plants AND meat is considered omnivorous (an omnivore).

Are animals that eat mostly grass and other plants

A herbivore is an animal whom only eats plants and not meat.