WHAT IS A CSA
There are a lot of explanations of what a CSA or farm share is.
I just wanted to share my understanding, based on 4 years of membership and all the varied CSAs that I've contacted or read about for this site. First off, CSA stands for 'Community Supported Agriculture', but is often called a 'farm share'.
A CSA is an agreement between a consumer (or set of consumers) and a farmer to purchase agricultural goods at a fixed price. The quantity and quality of the goods are not known at the time of purchase, though estimates are usually given. If the farmer has a bumper crop, the CSA shares will be plentiful; the opposite is true as well.
The benefit to the farmer is quite clear--they get capital when they need it, as well as a captive market so they can achieve some kind of scale. Consumers get many benefits as well--I've outlined them in 'why join a csa'.
And if you want, here's Wikipedia's definition of a CSA.