Grotesque is a type of fancy decoration used on buildings a long time ago. It was very popular during the Renaissance time period (that's a long time ago, even before mommy and daddy were born!).
This kind of decoration was really silly and fun. It often included monsters, animals and people with really weird faces. They were drawn in a way that made them look like they were twisted around and jumbled up, like a puzzle that doesn't fit together quite right. Sometimes, they even had plants and vines growing out of their mouths and eyes!
The people who made these decorations were very talented artists, and they would put their artwork on the sides of buildings or walls. Some of the most famous examples of grotesque are on old castles and churches in Europe.
So, if you ever see a building with funny-looking monsters or people on the walls, that's called grotesque architecture! And it's actually a really cool way to decorate a building.