Why do people flock to watch the trial? How does Jem describe them?

People flock to the courthouse, eating outside, and awaiting news because they are curious. The trial has become a show for the locals... something different and obsessive.

It was a gala occasion. There was no room at the public hitching rail for another animal, mules and wagons were parked under every available tree. The courthouse square was covered with picnic parties sitting on newspapers, washing down biscuit and syrup with warm milk from fruit jars. Some people were gnawing on cold chicken and cold fried pork chops. The more affluent chased their food with drugstore Coca-Cola in bulb-shaped soda glasses. Greasy-faced children popped-the-whip through the crowd, and babies lunched at their mothers’ breasts.

We knew there was a crowd, but we had not bargained for the multitudes in the first-floor hallway. I got separated from Jem and Dill, but made my way toward the wall by the stairwell, knowing Jem would come for me eventually. I found myself in the middle of the Idlers’ Club and made myself as unobtrusive as possible. This was a group of white-shirted, khaki-trousered, suspendered old men who had spent their lives doing nothing and passed their twilight days doing same on pine benches under the live oaks on the square.

As far as Jem's descriptions, are you referring to Scout's questions and Jem's answers? I have used the descriptions in Chapter 16 of the text.