Dear student,
A food chain is a sequence of eating and being eaten in an ecosystem.
The various steps in a food chain represent various trophic levels.
Eg. In a grazing food chain
1. Producers (Green plants)
2. Herbivores (Rabbit)
3. Carnivore (Snake)
4. Top carnivore (Eagle)
These four levels represent the various trophic levels.
Regards.