Trophic levels are different steps of a food chain. A trophic level is the level of species in an ecosystem on the basis of the source of nutrition such as producers, primary consumers, secondary consumers etc.
The producers form the first trophic level as they manufacture food.
The primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.
Terrestrial food chain :
Grass → Deer → Lion
(Producer) (Herbivore) (Carnivore)
1stTrophic level 2nd Trophic level 3 rd Trophic level