The concept is simple: people donate stuff they don't need and people who need the stuff take it. The free store is not a charity but rather a preventative practice. Charity becomes a benevolent band-aid to capitalism's downtrodden; instead, the free store works as an alternative economic system based on mutual aid.
The problem for capitalism: cooperation can’t be measured in economic profit. Capitalism suffers from cooperation (for example, communal living) because when people share resources, the need for production and consumption decline.