PPC stands for Pay Per Click and SEO stands for Search Engine Optimization. Whenever you search in Google, the first results, marked as Ads, are PPC. Then you have the maps listings, then the SEO, or organic results.
The main difference (besides location in search) is that traffic generated from SEO clicks is free, where traffic generated from PPC is not. With PPC, we are able to laser target specific customers and set a budget for each day, while running ads and paying per click. With SEO, we optimize your website to appear in organic search results. These are not limited by budget, and do not stop once your budget runs out.
The best strategy for ultimate online visibility is an integrated approach using both SEO and PPC. By doing both, you can dominate the first page searches, appearing multiple times and building brand credibility, trust, and increasing your chances of clicks.