After you're involved in a crash, you stay at the scene to call for help. When you look up to get the information you need from the other driver, all you see is the tail-end of his vehicle as he flees.
The driver leaving the accident is a hit-and-run driver. Leaving the scene of an accident is a terrible idea except for in very few situations, like when the scene itself is hazardous. Even then, the individuals involved in the crash have to stay close by.
It's a misdemeanor hit-and-run when a driver flees the scene in most cases so long as there are no physical injuries. However, since you were hurt in the crash, the driver may face a felony hit-and-run charge. This charge can lead to imprisonment and fines of up to $10,000. That's not considering the compensation you'll seek from the driver or his or her insurance carrier.
After the driver leaves the scene, try to remember all you can about his or her license plate, the type of vehicle and which direction he or she was heading. This helps the police find the driver, who, at this point, likely has a warrant out for his or her arrest.
As someone hurt by the hit-and-run driver, having a police report that shows the driver fled does help your case and gives your attorney leverage when negotiating with the insurance company. Your attorney can talk to you more about what will happen when the hit-and-run driver is found and what you can expect as far as compensation for your pain and suffering.
Source: FindLaw, "Leaving the Scene of an Accident: What Can Happen?," Betty Wang, JD, accessed May 25, 2017