What is food chain? what are herbivores, carnivores, omnivores and decomposers, and how are they linked in a food chain?

Food chain - A hierarchical series of organisms each dependant on the next source of food

Herbivore - organism that eats plants

Carnivore - organism that eats meat

Omnivore - organism that eats plants and meat

The Herbivore gets the plants, the carnivore eats the Herbivore, the Omnivore eats either

The Omnivore is at the top of the food chain, the Carnivore is in the middle the Herbivore is on the bottom