Each step or level of a food chain where transfer of energy occurs are called trophic levels.
Let us consider the following food chain.
In this food chain, grass is a producer (first trophic level). Insect is a herbivore and eats grass. Thus, insect is at second trophic level. Insect, in turn, is eaten by frog (carnivores I). Thus, frog is at third trophic level. Frog, is eaten by snake (carnivores II). Thus, snake is at fourth trophic level. Snake, in turn is eaten by peacock (carnivores III). Thus, peacock is at fifth trophic level.