A bull call spread, or bull call vertical spread, is created by buying a call and simultaneously selling another call with a higher strike price and the same expiration. The spread is profitable if the underlying asset increases in price, but the upside is limited due to the short call strike. The benefit, however, is that selling the higher strike call reduces the cost of buying the lower one. Similarly, a bear put spread, or bear put vertical spread, involves buying a put and selling a second put with a lower strike and the same expiration. If you buy and sell options with different expirations, it is known as a calendar spread or time spread.
When buying or selling options, the investor or trader has the right to exercise that option at any point up until the expiration date - so simply buying or selling an option doesn't mean you actually have to exercise it at the buy/sell point. Because of this system, options are considered derivative securities - which means their price is derived from something else (in this case, from the value of assets like the market, securities or other underlying instruments). For this reason, options are often considered less risky than stocks (if used correctly).