“Affiliate marketing is a useful skill because it allows you to monetize your website or blog traffic,” said Drew Mann, founder of Drew’s Review. “If you have a website or blog with a large audience, affiliate marketing can be a great way to generate revenue from that traffic. Additionally, affiliate marketing is useful because it allows you to promote products and services that you believe in and use yourself. This builds trust with your audience and can help increase sales of the products or services that you promote.” 

Mann added that the amount of money you can make with affiliate marketing varies depending on the program you choose, the products you promote and the amount of traffic you can generate; “however, some affiliate marketers earn thousands of dollars per month.”

Source: https://www.gobankingrates.com/money/jobs/best-skills-to-learn-to-make-money-online/