motorcade
A line of vehicles traveling together, usually for an important person.
A motorcade is a procession of vehicles traveling together, usually to transport an important person safely from one place to another. When the President of the United States travels through a city, you might see a long line of black cars, police motorcycles, and security vehicles moving together in formation. That's a motorcade.
Modern motorcades often include police escorts at the front and rear, ambulances in case of emergency, and specially armored limousines for the VIP being protected. Security teams plan the exact route in advance and sometimes block off streets so the motorcade can move quickly and safely.
You might see motorcades for visiting presidents, foreign leaders, or other dignitaries. Some cities also have motorcades for special celebrations, like when a sports team wins a championship and parades through downtown with their trophy. The key feature is that all the vehicles move together as a coordinated group, not scattered randomly through traffic like regular cars.