Is it possible to make players deal damage on their team members but not other teams?

I have a game that has a 'PvP' team and a 'Lobby' team. Basically the PvP team can deal damage on players that are also in the PvP team but not the Lobby team. I've tried to find help and make a script for it however, I'm just stuck. If this IS possible can somebody point me into a direction that can help?

I'm using the classic Roblox sword, I'm positive I have to change the damage properties and that's where I'm stuck. I'm completely new to this and I'm trying to learn at the same time.