Paid traffic is the opposite of organic traffic. This is the traffic you get from advertising systems like AdWords, and (no surprise here) you have to pay for. You shouldn’t really think of it as “buying traffic,” however, because you can’t actually do that. You are “bidding” for the right to have your ad shown to a searcher, and then that person decides if they want to click on your ad and become traffic to your website. So “paid traffic” is not a term that you’ll hear very often, but when you do, it is usually used in conversations about AdWords versus organic SEO.