The barricades are like a big wall made out of stuff that people use to block things off or protect themselves. It's like building a really strong fort made out of boxes or furniture to protect yourself from something scary, like a monster or a bad guy.
In history, people used barricades during times of war or protests to protect themselves and hold their ground. Sometimes they would build the barricades out of old carts, furniture, and anything else they could find on the street. The barricades would block people or vehicles from entering certain areas or protect the people inside from attacks.
Today, we still use barricades for similar reasons. You might see them used on construction sites to keep people away from dangerous areas, or during big events to keep crowds under control. They also sometimes use them for safety on roads and highways to prevent accidents or keep people from driving into dangerous areas.