Freeganism is the practice of minimising one's impact on the environment by means of consuming food that has been thrown away by someone else (e.g. supermarkets).
Acting this way, a freegan has no responsibility for the material and energy resources used in the production process, since the goods have already exited the production-consumption cycle where money is used in exchange for goods.
In most developed countries, the quality demands and hygiene standards of consumers are so high that many foods stay perfectly edible for long periods of time after their expiry or "best before" dates. Naturally, the best seasons for freeganism are autumn and spring, when waste bins remain at refrigerator temperatures.
Many people practicing this diet have been forced into it simply by lacking the income necessary to purchase food normally, rather than making a conscious decision to sustain themselves by scavenging when other choices are available.
Freeganism is also used to describe people who are vegan, 'unless it's free.' Unlike the above, these people do not necessarily eat food that was already thrown away, but rather they eat non-vegan food that is offered to them, or that would otherwise be thrown away. However, they may often have the same motives, or they may simply be acquiescing to their friends, relatives, or coworkers attempts to feed them non-vegan food.