Why do you need SEO?
Your customers use search engines like Google or Yahoo! to find products and services. The main objective of SEO is to get your website ranked in the natural or "organic" section of search engine results. Because you have to earn your way there, being listed in natural search engine results is a sign of credibility. People trust natural search results, but unless your site is near the top of the search results, customers are unlikely to see your website.
Pay Per Click Advertising vs. SEO
When you enter a keyword at a search engine like Google, you get back two types of results - paid search ads or "sponsored listings" and natural or "organic" results. PPC works together with Search Engine Optimization (SEO) to give you immediate visibility in the sponsored listings, while you are building your natural search results.