Personal Goals are the motivating reasons your characters care about and/or participate in the effort to achieve or prevent the overall goal. In other words, they see the main story goal as a means to an end, not as an end itself.
Although a personal goal for each character is not absolutely essential, at some point your audience or readers are going to wonder what is driving each character to brave the trials and obstacles. If you haven’t supplied a believable motivation, it will stand out as a story hole.