norton family browser plug has stopped working-what does this mean? what is the plug in??

i keep getting this below sent to me about my sons computer-what is the plug in??

 

 

The Norton Family browser plug-in was unexpectedly turned off on  your computer               . This plug-in will be re-enabled automatically in five minutes. If it does not restart automatically, restart the browser or computer. The following features require the plug-in:

  • Safe Searching
  • Social network monitoring
  • Video monitoring (Premier Members)