Organic or natural search engine optimization refers to fine tuning your web site, optimizing keyword saturation and in a small way also meta tags in your pages so that the major search engine spiders will be able to easily spider and index your site in the natural or organic search results. This gives you high rankings at the search engines for your chosen search terms.
Organic search results appear in left side and PPC search results appear in right side, you can check this below the reference.
According to the report, searchers click the organic search engine results 60% more than the PPC advertisements, so you'll get much more traffic for less.

The golden rule in marketing is that you should constantly strive for maximum results and ROI for your budget. In other words, if your marketing is making you a profit - even if it's a thin profit - it's worth it. By this model, pay per click is worth doing, but overall pay per click will leave you with thinner margins. The reason for conducting a organic search engine optimization campaign is to significantly increase your margins over the long term. Therefore, you should focus on natural SEO services.