An out-of-the-money option is an option that would be worth nothing if it were exercised now, one of the states of moneyness set out in the main entry on in-the-money and out-of-the-money options. A call is out of the money when the underlying trades below the strike price, and a put is out of the money when the underlying trades above it. With a share at 108, a call struck at 115 and a put struck at 100 are both out of the money.
Such an option has no intrinsic value, so its whole price is time value: what buyers will pay for the chance that the underlying moves past the strike before expiry. It is cheaper than an in-the-money option on the same underlying and has a smaller delta, so it responds less to each move in the underlying but gains more in percentage terms if a large move arrives.
This makes out-of-the-money options the usual choice for low-cost speculation and for protection against extreme moves, and the usual options sold in strategies that collect premium, such as the iron condor. An option that is still out of the money at expiry lapses worthless, and the buyer loses the premium paid.