A lot of illegal activity comes with a basis around personal gain, but may be committed due to desperate circumstances. While someone robs a store in order to get something for free another person might steal to pay their family's bills. One person will break the speed limit to get to their destination faster while another races to make an important appointment.
In criminal cases, there are two types of juries. These each serve a different purpose but are both important to the process. It is helpful to understand the differences so that you have a better idea of what is going on.