!!!...Tough Language...!!!

In the big city, there lots of people that speak aliens languages. It's English word but It doesn't sounds right. Sometimes, I saw some tough guy say something in English but I don't understand what are they trying to say. I heard from someone that he saw a tough guy shout "blue square" to sell something. He thought maybe he trying to sell drug. Later, he found out that "blue square" is a cigarette. I don't know that in a big city why they have to use language that many people doesn't understand. Why they have to make it harder? . Somebody please help me to find the answer.