This is the term used in many jurisdictions to describe—in a construction project involving a historic resource—adherence to Secretary of the Interior’s (SOI) Standards.
Secretary of the Interior’s Standards
These were originally a unitary list of 10 Standards for Rehabilitation in the early era of adaptive reuse, when over-restoration made many historic resources look not very historic. Now the SOI Standards have been divided into 4 lists of 6 to 10 standards each:
Standards for Preservation (8), Rehabilitation (10), Restoration (10), and Reconstruction (6).
This looks more complicated, but most of the standards are repeated across the first three categories (reconstruction of vanished historic structures being an odd and rare case). This link shows all four sets of standards in comparative columns.
The main thrust of SOI Standards is similar to the part of the Hippocratic Oath that says, “First, do no harm.” Keep as much as possible of a structure’s original design, materials, and workmanship—the physical integrity—in preserving it, rehabilitating it from decay, or restoring it to a particular period of significance. Use documentation and physical evidence. Make documentation, so people in the future know what you’ve done and why.
For the average owner of a historic house, day-to-day preservation is unlikely to come under public purview. City employees and historic preservation commissions usually appear when changes are proposed, e.g., new windows, sometimes new roofing, room additions, accessory dwelling units (ADUs). The most common standard that an owner of a historic house encounters is No. 9 in Rehabilitation, regarding additions, exterior alteration, and related construction: do not destroy characteristic material, features, or spatial relationships, and make sure new work is differentiated from, but compatible with, historic materials, features, size, scale, and massing. In other words, an addition or ADU should not be mistaken for being historic, but it shouldn’t clash with or overwhelm the historic core.