A food chain is a series of organisms which eat one another. And in this food chain at each level specific type of organisms occupy the same level. Hence, the trophic level is the position of a group of organisms in a food chain. It refers to the mode of nutrition at every different trophic level.

For example Plants (producers) get their nutrition from sunlight and prepare their own food. Then comes the consumers (herbivores) they cannot prepare their own food hence get their nutrition by feeding on plants. Then comes the secondary or tertiary consumers (carnivores) they get energy by eating other animals. They all get the nutrition from the organisms of lower trophic levels.