A motorcade is a line of cars driving together, one behind the other, carrying someone important — a president, a king, a visiting leader — along with the guards, the officials, and often police motorcycles in front clearing the way. You see it on the news: the road is closed, the lights flash, and ten or twenty black cars go past without stopping. The word carries that whole picture, not just 'some cars'. Two things make a motorcade a motorcade. First, there is an important person inside one of the cars. Second, the cars move as one group, on purpose, usually with protection. So a traffic jam is not a motorcade, and neither is a line of cars going to a wedding — though a funeral has its own word, a funeral procession or funeral cortège. The word is much more common in American English and in news writing than in daily conversation; British reporters use it too, but you would rarely say it to a friend. If you did want to say it plainly, you would say 'the president's cars' or 'the convoy'. Note that 'convoy' is the broader word — a convoy can be trucks carrying food or soldiers, with no important person at all.