Many small businesses credit SEM for attracting new customers. Depending on the competition in your business, relying on unpaid, organic Web traffic via SEO may leave your business far back in the rankings. By paying for SEM, you have more control over the specific keywords that will promote you, as well as where you will appear on the search results page.
Organic traffic is the traffic you get when people follow links from a search engine results page and land on your site. Organic traffic contrasts with referral traffic which comes from links on other sites, and paid traffic, which is traffic resulting from ads. You can boost organic traffic by using content marketing, and by optimizing that content with SEO. Well-optimized content is more likely to get a high search ranking, and attract more clicks and traffic.
Use Google. Google Adwords is the most popular method for traffic. Since they are the top search engine right now it make sense to advertise there if you can afford it. You bid on keywords to get your site at the top of the search when your keyword comes up. There is more involved but it's all laid out at Google. There are a lot of other sites that use this advertising strategy called pay per click or PPC.