You've probably heard of affiliate programs. Companies use affiliate programs to sell their products. The most common way for making money online with affiliate programs is through posting a link on your website. When a customer clicks on that link and buys the product, you earn a commission.
There are many advantages to making money online with affiliate programs. Startup costs are minimal. The only money you spend is to promote the product, whether through a website or other means. You don't actually sell the product, so you don't spend time shipping the products or money to buy them at wholesale prices, hoping to sell them later. Another advantage is that you don't have to worry about unsatisfied customers returning the product to you.
A good way to start making money online with affiliate programs is to find a subject you are interested in and start a website. After the website is up, find companies that sell this product and register to be an affiliate. They will give you some code to paste in your website. You can use text codes or pictures, but text code seems to be the most effective for converting to sales.
Look at websites in your area of interest. For example, if you are interested in music, look at sites devoted to your favorite musicians. Study them to see how they place ads. Notice your responses to those ads. Some are annoying, but others will make you want to click through. Learn from this and place ads similar to those that interested you.
Starting a website devoted to something you love is rewarding. If you need some extra money, making money online with affiliate programs can be a useful addition to something you already enjoy.