Definition
A Greenfield facility is a facility that does not currently exist in the scenario but will be created by a solver to meet certain criteria.
The new greenfield facility will be a clone of an existing model facility in that it will have the same characteristics (in terms of activities, supply, and capacity) as the facility you choose to clone. Alternatively, the facility can be a default version of another facility in your model (i.e., a new Warehouse, Plant, etc.) which will be able to supply all products to all customers.
Usage
You can use Greenfield facilities in all solvers except for "Solve for...".
A Greenfield analysis is useful for finding the absolute best location for a facility without being constrained by the existing choices in your model. It serves as a useful comparison for the solution you would obtain from using only your existing facilities, since you can compare how close to the absolute optimal solution you are with your existing network.