Farmstadts are a hypothetical construct in the Plan, and are aimed at providing self-sufficiency, safety, and other amenities to the supporters of the plan and the members of its branches.
They would be designed to survive a collapse and also provide refuge for outsiders who may be adversely affected by a potential collapse. They would akin to a settlement of sorts, and would be protected against various outside threats. These Farmstadts would ideally be built up in the pre-collapse world.
Further information on Farmstadts is freely available on the official YouTube channel
Playlist with the plan video series (Part 7)
Plan text document version (Part 7)
Concept drawing for Farmstadt