PPC (paid search marketing): PPC (pay per click) advertising involves paying to have search engines display your website offer in or alongside search results. For example, Google's Adwords program will display your ad at the top or right side of the search results page (placement depends on many factors including keywords and quality of ad). Google will also feed your ads to websites running its Adsense program. There are other types of PPC marketing, such as Facebook Ads. In PPC advertising, you pay each time someone clicks on your offer. Paid search differs from organize search in that you're paying to have your website or offer displayed higher in search results.
Remember when you used to rely solely on search engines for traffic? Remember when you worked on SEO and lived and died by your placement in Google? Were you #1? Assured success. Well, okay, maybe not assured. Success only came if the keywords were relevant to your site users, but it was the only real roadmap to generating site traffic and revenue.