These four approaches to historic buildings are defined in the Secretary of the Interior’s Standards for the Treatment of Historic Properties.
Preservation: places a high premium on the retention of all historic fabric through conservation, maintenance, and repair. It respects a building’s continuum over time, and through successive occupancies, and the respectful changes and alterations that are made.
Rehabilitation: emphasizes the retention and repair of historic materials, but more latitude is provided for replacement because it is assumed the property is more deteriorated prior to work.
Restoration: focuses on the retention of materials from the most significant time in a property’s history, while permitting the removal of materials from other periods.
Reconstruction: establishes limited opportunities to re-create a non-surviving site, landscape, building, structure, or object in all new materials.
Source: National Park Service: The Secretary of the Interior’s Standards for the Treatment of Historic Properties, Introduction ” Choosing an Appropriate Treatment for the Historic Building”
see also: Introduction: Using the Standards and Guidelines for a Preservation, Rehabilitation, Restoration, or Reconstruction Project.”
Another excellent source for information on this topic is the Historic Preservation Services, National Park Service, Technical Preservation Services for Historic Buildings:
Secretary of the Interior’s Standards for the Treatment of Historic Properties
This source provides helpful information for choosing a treatment and the scope of work involved in each.