Food chains
Food chains show the transfer of energy from one organism to another. 
Primary Producer --> Primary Consumer --> Secondary Consumer --> Tertiary Consumer --> Quatemary Consumer


Example:

Food webs
A system of interlocking and interdependent food chains.

Example:

Trophic levels
The trophic level is the position that an organism occupies in a food chain. Each feeding level in a food chain is called a trophic level.