The function of Search Engine Marketing is mainly divided into two main areas that are Organic Search Engine Optimization and Pay-Per-Click Marketing. The main objective of both the strategies is to help your website to be listed on top of the search engine results pages (SERPs).
Pay-per Click Marketing is like traditional advertising. In this type of advertising you pay only when someone actually clicks on your advertisement and that is the reason it is called Pay per click.
Organic SEO is more like public relations where you have to work like making changes to your website to include targeted keywords and phrases and increasing the number of qualitative incoming links to your website.
The most important difference is the cost. That is under PPC strategy you are liable to pay for the clicks on your ads while clicks on SEO are free. So getting on top of SEO results require hard work while to get on top in PPC requires money. Organic Search engine rankings are more cost-effective comparatively.
PPC is a quick process to get the traffic to your website if you are willing to pay for clicks. You can easily buy a top position for your search terms in major pay per click engines. While Search Engine Optimization is a slower process and the results can be seen in a long run. PPC results can start showing up within 48 hours while organic search results can take 6 months or even more.
The effects of SEO are long lasting and less costly compared to PPC. The day you stop your pay per click campaign, the traffic will vanish while SEO will continue to bring traffic even if stop SEO work on the website.
PPC and SEO are two complementary strategies and if both are used then there is no harm. In fact, if both used together they will be more successful rather than using just one or the other alone.