If you are looking to drive more traffic to your site and increase your revenue, both PPC and SEO campaigns can be good ideas, depending on your market situation.
The main difference lies in how these two different sorts of campaigns help you achieve your SERP rankings.
PPC advertising campaigns depend on you constantly having a budget, paid to one of the major search engines’ pay-per-click programs. Google AdWords is the most commonly used PPC provider.
SEO results, on the other hand, are built up organically, and will remain over time. The catch is that they are harder both to initially achieve and to maintain. Maintaining organic results over time requires that you constantly be adding new content to your site, optimized specifically around the words you are looking to rank for. On top of that, you need a link building campaign designed to support the content. PPC results are instantly achievable, but cost more.
To sum up, SEO takes time to build and execute properly, but organic results last longer and don’t require a per-click investment on your part.