RBXScriptConnection

The RBXScriptConnection data type is a special object returned by the Connect() method of an event (RBXScriptSignal). This is used primarily to disconnect a listener from an RBXScriptSignal.

local part : BasePart = script.Parent
-- Store reference to the RBXScriptConnection so it can be disconnected later
local connection : RBXScriptConnection = part.Touched:Connect(function(otherPart)
    print("Hello world!")
end)
-- Wait 15 seconds, then disconnect
task.wait(15)
connection:Disconnect()