Short answers, pulled from the story.
Reconstruction in architectural conservation is the process of returning a place to a known earlier state by introducing new materials. Under the United States Secretary of the Interior's Standards, it is formally defined as depicting, using new construction, the form, features, and detailing of a non-surviving site, building, or structure to replicate its appearance at a specific time and in its historic location.
There are at least six recognised types: true-to-the-original reconstruction (same materials and methods, extensive source research); modelled reconstruction (filling gaps with inference from similar buildings); replicative reconstruction (imitating a historical style for functional reasons, without connection to the original); interpretive reconstruction (capturing overall character without one-to-one copying); didactic reconstruction (for archaeological theme parks); and experimental reconstruction (such as Guédelon Castle, built since 1997 using only 13th-century techniques to study medieval methods).
The reconstruction of Warsaw's historic city centre is the most widely cited example. German troops systematically razed the Old Town after the Warsaw Uprising of 1944, and the subsequent rebuilding of structures including St. John's Cathedral, St. Kazimierz Church, and Ujazdów Castle was recognised by UNESCO as a World Heritage Site, a rare acknowledgment that a reconstruction can carry heritage legitimacy.
The Venice Charter of 1964 is the most important monument conservation text of the 20th century. It established central values and procedures for the conservation and restoration of monuments, emphasising the preservation of authentic original building fabric over the recreation of historical appearance.
Japan's Ise-jingu Shrines have been ritually rebuilt every 20 years according to the same wooden plans for roughly 2,000 years, in a tradition that regards material as secondary to form. In China, entire historic districts have been removed for major development projects while historicising rebuilds are simultaneously pursued. The European insistence on original material is largely absent from these traditions.
A representative survey by the Forsa Institute, commissioned by the German Federal Building Culture Foundation, found that 80% of participants supported the reconstruction of historic buildings, with 15% opposed. Support was highest among 18-to-29-year-olds at 86% and among women at 83%.