In a bull call spread, you buy a call on the underlying asset while simultaneously
writing (selling) a call on the same underlying asset with the same expiration month
at a higher strike price. You should use it when you think the market will go up
somewhat, or think it’s more likely to rise than fall (in other words, you have
a bullish or moderately bullish outlook). Your likelihood for profit is limited,
as is your risk, because the price paid for the call with the lower strike price
is partially offset by the premium received from writing the call with a higher
strike price, so you have less risk of losing the entire premium paid for the call.