Explain what affiliate marketing is, how it works, and why it's a popular online business model.

Affiliate marketing is a type of performance-based marketing strategy that involves a business rewarding one or more affiliates for each visitor or customer brought by the affiliate's own marketing efforts.

Here's how it works, step by step:

1. An affiliate signs up to be a part of the affiliate program of a merchant or advertiser.
2. The affiliate gets a unique link or affiliate ID that tracks the traffic that they send to the merchant's site.
3. The affiliate promotes the merchant's products or services by placing the link on their website, blog, social media posts, or other platforms.
4. When a visitor clicks on the link and makes a purchase or completes a desired action on the merchant's site, the affiliate earns a commission.

Affiliate marketing is a popular online business model for several reasons:

1. Low start-up costs: Unlike traditional businesses, you don't need a lot of capital to start an affiliate marketing business. All you need is a website or a blog, which can be set up at a minimal cost.

2. Passive income potential: Once you've set up your affiliate links and the traffic starts flowing, you can potentially earn money while you sleep. This is because you earn a commission every time a purchase is made through your link, regardless of the time of day.

3. Flexibility and independence: As an affiliate marketer, you have the freedom to choose what products or services to promote, and you can work from anywhere and set your own hours.

4. Scalability: With affiliate marketing, your earning potential is not limited to the number of hours you work. As you build your website and attract more traffic, your income can grow exponentially.

5. No customer support: Unlike other business models, as an affiliate marketer, you don't have to deal with customer support or product fulfillment. The merchant handles all of that.

In conclusion, affiliate marketing is a popular online business model due to its low start-up costs, passive income potential, flexibility, scalability, and the fact that affiliates don't have to deal with customer support or product fulfillment.