Positive for calls, negative for puts - a higher rate reduces the present value of the strike you will pay, which helps a call and hurts a put.
Usually the least important Greek for short-dated equity options, where a rate change moves the price far less than a move in spot or volatility.
When it matters: long-dated options, where discounting over years is material; rates products, obviously; and any period of large rate moves, when the assumption that rho is negligible quietly stops holding.