There are two basic categories of nutrition: autotrophic and heterotrophic. Biologists look at two main resources (energy and carbon) and how organisms acquire these resources in order to classify which category every organism fits into.
Literally meaning other-feeders, heterotrophs are organisms that cannot produce the nutrition they need by themselves. Instead, they must receive carbon by ingesting organic compounds. In other words, heterotrophs eat other organisms/organic compounds to survive.
One subcategory of heterotrophs are the photoheterotrophs. These organisms are similar to plants in that they both obtain their energy from the sun. Dissimilar to plants, photoheterotrophs still need to receive carbon through other organic compounds while plants get their carbon from CO2.
A second subcategory of heterotrophs are the chemoheterotrophs. These organisms receive both their energy and carbon through organic compounds. An example includes E.coli, a microorganism that lives in human intestines. E. coli can survive on a plethora of different organic nutrients (such as glucose).
Although most prokaryotes are heterotrophs, the organisms that usually come to mind when thinking about heterotrophs are animals. All animals, in fact, happen to be heterotrophic organisms. Humans are a great example of heterotrophs because both you, and I, and everyone else reading this post happen to be one! As we all know, humans must eat other organisms (such as plants, other animals, etc) for survival. A human’s food supply has been chosen to depict the definition of a heterotroph. This particular food supply includes many healthful foods such as spinach, strawberries, and the like. It even includes the all-important cookie-dough ice-cream, which some humans have been reported to say they cannot live without.