The Difference Between Classical and Neoclassical Architecture

"Neoclassical" architecture has been a buzzword lately due to a recent Executive Order mandating all federal buildings be built in the neoclassical style.

So what exactly is neoclassical style and how does it differ from classical architecture?

The classical period occurred from about 8th century BC to 6th century AD and is often referred to as "antiquity." It was a historical period dominated by the ancient Greeks and Romans, and for this reason, the artifacts and culture were often referred to as "Greco-Roman."