Tell me more instead of this:
game.StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Health,false)
CoreGuis are Roblox made GUIs, like healthbar, backpack, and the leaderboard. The script you have there would make the healthbar invisible.
CoreGUIs are basically, the leaderboard/player list, Health, chat log and chat bar. To hide them you could do this:
game.StarterGui:SetCoreGuiEnabled("All", false)