Food chain is the process of who eats whom . It is the cyclic process of eating where large animal feed on small one and small animals feeds on resources available or on anything .
For example :-
Grass-- grasshopper-- frog--snake -- vulture .
Here , grasshopper feeds on grass , frog eats grasshopper and further eaten by snake and lastly snake is eaten by vulture. Here the cycle of who eats whom can be clearly defined . Here grasshopper is primary consumer and vulture is highest consumer .
This food chain is very important for maintaining the balance of environment if this process will stop the organism will not survive due to shortage of food. Also the number of species will be increasing rapidly day by day.
Thus, food chain maintenance the number of species. Several food chains will constitute one food web where one animals can be eaten by several animals .
Hope you will be satisfied with my answer.
Thank you!!