Hellenism or neoclassicism is a fancy word for a style that people started liking a lot around 200 years ago. This style was inspired by the ancient Greeks and Romans, who were some really smart people who lived a long time ago.
Have you ever seen a big fancy building with columns in front and a triangular roof, like at a bank or courthouse? That design was inspired by the Greeks and Romans. They made lots of buildings like that a long time ago.
Neoclassical design was also used for things like furniture and art. People really liked how the ancient Greeks and Romans made things, so they started making things in that style too.
Even today, some people still like to use neoclassical designs for buildings or other things. It's a way to make things look very fancy and important, and it all started because people liked the way the ancient Greeks and Romans did things.