Real time tracking means that you can track your child anytime, anywhere, seeing their exact location on a map. This is opposed to tracking mechanisms that can only be activated in case of emergencies, and may not be accessible by the parents themselves.
This is often web-based, allowing the parent to track their daughter or son on a web app on their cell phone, at work on the computer, or something along those lines. The idea is that the parent can know where their child is at anytime, no matter what.