Who doesn’t want to earn more money? Whether it’s through part-time jobs or freelance work, adding more dollars to your cash flow every month is always nice. But unfortunately, not everyone has the time to pick up another job or do additional work on the side. If that’s the case for you, don’t give up. Instead, turn to the one thing you probably spend a majority of your time on: the internet.
Let’s say you have a promotions page where you’re promoting a product via affiliate links. If you currently get 5,000 visits/month at a 2% conversion rate, you have 100 referrals. To get to 200 referrals, you can either focus on getting 5,000 more visitors, or simply increasing the conversion rate to 4%. Which sounds easier? Instead of spending months building domain authority with blogging and guest posts to get more organic traffic, you just have to increase the conversion rate by 2%. This can include landing page optimization, testing your calls-to-action, and having a conversion rate optimization strategy in place. By testing and optimizing your site, you’ll get far better results with much less effort. 
While these models have diminished in mature e-commerce and online advertising markets they are still prevalent in some more nascent industries. China is one example where Affiliate Marketing does not overtly resemble the same model in the West. With many affiliates being paid a flat "Cost Per Day" with some networks offering Cost Per Click or CPM.
Analytics are limited. Unlike with conversions made directly on your WordPress site, you’ll be limited in terms of what you can learn about the people making purchases through your affiliate links. While Amazon does provide you with details about clicks and sales, you won’t get deep insights into who the consumer was and what they did on your site before they got to that point that you would with Google Analytics.