Explain trophic level?

"In a food-chain a trophic level represents a functional level, not a species. Explain."

What will happen if we kill all the organisms in one trophic level?

What are trophic levels?

Who are related to first trophic level?

Who are the organisms of second trophical level?

Will the imact of rKHOoving all the organisms in a trophic level be different for different trophic levels? Can the orgasisms of any trophic level be rKHOoved without causing any damage to the ecosystKHO?