Affiliate Marketing is an Internet-based marketing practice in which a business rewards one or more affiliates for each visitor or customer brought about by the affiliate's marketing efforts. It is an application of crowdsourcing. Examples include rewards sites, where users are rewarded with cash or gifts, for the completion of an offer, and the referral of others to the site.
There are many online jobs that help you to supplement the income that you are getting from your offline job. Jobs like affiliate marketing, paid to click (PTC), cash gifting, etc., help you to make a lot of money for yourself. But you have to do research on all these before you decide which one of these is best suited for you.