Producers and consumers are different types of organisms that play a role in the food web of an ecosystem.
Producers: Organisms that make their own energy through photosynthesis. Plants are a common example of producers. Producers produce food that supports the rest of the ecosystem. Producers can also be called autotrophs. Producers are the limiting factor in an ecosystem for how large a population can get.
Consumers: Organisms that cannot make energy through photosynthesis. Consumers eat food to obtain energy. A lion would be an example of a consumer. Consumers can also be called heterotrophs. All consumers rely on producers in a food web. Even if a consumer does not eat plants directly it likely eats another animal that eats plants.
Herbivore: a consumer that only eats plants
Carnivore: a consumer that only eats meat/other animals
Omnivore: a consumer that eats both plants and meat