According to Wikipedia:
Community-supported agriculture (CSA; sometimes known as community-shared agriculture) is an alternative, locally based economic model of agriculture and food distribution. A CSA also refers to a particular network, or association of individuals, who have pledged to support one or more local farms, with growers and consumers sharing the risks and benefits of food production.
CSA members, or subscribers, pay at the onset of the growing season for a share of the anticipated harvest; once harvesting begins, they periodically receive shares of produce. In addition to produce, some CSA services may include additional farm products like honey, eggs, dairy, fruit, flowers and meat. Some CSAs provide for contributions of labor in lieu of a portion of subscription costs.
The term CSA is mostly used in the U.S. and Canada, but a variety of similar production and economic sub-systems are in use worldwide.