My touchscreen is still not responding even after reboot

What is a digitizer and how will I know if it needs replacing? Didn't know I needed to be an electronic wizard to own this device. Can a novice safely open the tab3 or should I find an electronics or Sprint store as Sprint is carrier of this particular device? I have rebooted to no avail. Has not been dropped or had any water on it. I charged it then went to input my pin to unlock and NOTHING extra pressure didn't work. Help