Producers are living beings at the beginning of the food chain. For example, plants are producers. Producers are always the first link in a food chain. Producers are living beings capable of producing their own living matter.
Consumers are living beings who can not produce their own organic matter alone. To grow and grow they need to consume other living things. For example, animals or humans are consumers. The primary consumer consumes the producers, and the secondary consumer consumes the primary consumers, and so on.
Decomposers are living things that degrade organic matter, transform it and return it to nature in the form of mineral elements. Decomposers are living beings responsible for "cleaning" the earth and recycling dead living organisms into organic matter that can in turn be consumed by producers. For example, maggots are decomposers.