The children, Scout and Jem, intervened and approached the mob at the jail where Atticus was guarding Tom Robinson. Scout's innocent conversation with Mr. Cunningham, one of the mob members, and her recognition of other men in the mob led them to disperse and retreat. Her presence humanized the situation and prevented any violence from occurring.
Scout recognized Mr. Cunningham in the mob and engaged him in conversation about his son, which humanized Atticus in Mr. Cunningham's eyes and helped diffuse the situation. This act of empathy and understanding ultimately led to the mob dispersing and Atticus being saved.
The children hear Heck Tate asking Atticus if the mob is gone. Heck Tate is the Maycomb sheriff who tries to maintain order during the tense situation outside the jail where Atticus is protecting Tom Robinson.
Atticus explains the concept of a mob to his children by describing it as a group of people who act emotionally and without thinking rationally. He emphasizes the importance of maintaining one's individual conscience and not succumbing to group mentality. Atticus uses this example to teach Scout and Jem about standing up for what is right, even when others around you are behaving unjustly.
He doesn't. Atticus compares the men in the mob to animals.
Tom is in the Maycomb County Jail during the time that Atticus faces the mob downtown.
Boo Radley saved the children from Bob Ewell. Atticus thanks Boo because if Boo hadn't stepped in to stop Bob Ewell, the children probably would have been killed. Atticus is thanking Boo Radley for keeping his children alive. At least, that's how I see it :)
The Children finds Atticus in front of the maycomb jail.
scout
Because Atticus was trying to defend Tom Robinson and protect the mob from causing harm to him. They even had to change him to another jail because of the people of Maycomb trying to get at him. (They weren't so much after Atticus as they were trying to get him out of the picture, in order to hurt Tom Robinson...) I hope this helps a little :)
In chapter 15, the children find Atticus outside the Maycomb jail. He is sitting in front of the jailhouse door reading a book, keeping watch over Tom Robinson to protect him from a possible lynch mob.
To protect tom from the mob!
They found him at the courthouse in town. Tom Robinson had been moved there to await trial, and Atticus was afraid there would be trouble from the people who lived in Maycomb. He's right, as a mob shows up at the jail to come after Tom Robinson, which the children see, as they were there looking for Atticus.