An option remains valuable only if the stock price closes the option’s expiration period “in the money.” That means either above or below the strike price. (For call options, it’s above the strike; for put options, it’s below the strike.) You’ll want to buy an option with a strike price that reflects where you predict the stock will be during the option’s lifetime.
When buying a call option, the strike price of an option for a stock, for example, will be determined based on the current price of that stock. For example, if a share of a given stock (like Amazon (AMZN) ) is $1,748, any strike price (price of the call option) that is above that share price is considered to be "out of the money." Conversely, if the strike price is under the current share price of the stock, it's considered "in the money." 
Covered calls can make you money when the stock price increases or stays pretty constant over the time of the option contract. However, you could lose money with this kind of trade if the stock price falls too much (but can actually still make money if it only falls a little bit). But by using this strategy, you are actually protecting your investment from decreases in share price while giving yourself the opportunity to make money while the stock price is flat. 
Based on data from IHS Markit for SEC Rule 605 eligible orders executed at Fidelity between April 1, 2018 and March 31, 20198. The comparison is based on an analysis of price statistics that include all SEC Rule 605 eligible market and marketable limit orders of 100-499 shares for the 100 share figure and 100–1,999 shares for the 1,000 share figure. For both the Fidelity and Industry savings per order figures used in the example, the figures are calculated by taking the average savings per share for the eligible trades within the respective order size range and multiplying each by either 100 or 1000, for consistency purposes. Fidelity's average retail order size for SEC Rule 605 eligible orders (100 -1,999 shares) and (100–9,999 shares) during this time period was 430 and 842 shares, respectively. The average retail order size for the Industry for the same shares ranges and time period was 228 and 333 shares, respectively. Price improvement examples are based on averages and any price improvement amounts related to your trades will depend on the particulars of your specific trade.

An option is a contract that allows (but doesn't require) an investor to buy or sell an underlying instrument like a security, ETF or even index at a predetermined price over a certain period of time. Buying and selling options is done on the options market, which trades contracts based on securities. Buying an option that allows you to buy shares at a later time is called a "call option," whereas buying an option that allows you to sell shares at a later time is called a "put option."