A food web consists of all the different food chains in a particular ecosystem, better presenting the relationship of each living thing to another within that ecosystem. Since one living thing can be a part of multiple food chains, different food chains in a food web interconnect and overlap at different points.
Food webs and food chains are not different ways of understanding the relationship between living things in an ecosystem. Food chains show direct relationships, one possible path for nutrients to take in an ecosystem, while food webs bring all the food chains together.
In a food web, organisms are divided into three trophic levels. These categories divide all living things into producers, consumers and decomposers. Consumers are further subdivided into primary consumers, or herbivores; secondary consumers that eat herbivores; and tertiary consumers that eat secondary consumers. Some ecosystems may have more levels of consumers before the chain reaches its apex, or top predator.
The food web itself connects the different food chains, long or short, and different trophic levels. In a healthy food web, there are an abundance of producers, or autotrophs, many herbivores and a small number of carnivores or omnivores. This composition maintains the balance of the ecosystem and keeps it recycling its biomass, which is the total energy of all the living organisms in the web.