Answer:
Producer is an organism that produces it's own food e.g. photosynthesis in plants. Also known as the base of the food-chain.
Consumer is an organism that consumes (eats) either a producer or another consumer e.g. animals will solely eat plants (herbivore) , sole animals (carnivore), or a combination of both (omnivore).
Decomposers are organisms that 'eat' and break up dying/decaying material e.g. earthworms and fungi.