SEO: (search engine optimization) The process of optimizing HTML code of a website and choosing targeted keyword search phrases related to a site, then ensuring that the site places well when those keywords are queried on search engines.

SEM: (search engine marketing) is the process of bringing together several elements of modern day marketing as well as search engine optimization and applying both theologies to a website essentially pinpointing exact target markets and website conversion metrics to improve customer quality and conversion rates..

I like to think of search engine optimization as the broadsword of Internet marketing, and search engine marketing more so as a scalpel.

Back in 2000 - 2003 all a website needed was a solid SEO campaign and voila, your website is being bombarded by thousands of visitors derived from dozens of search phrases that your website had been optimized for. Then came the advent of thousands of SEO companies optimizing websites on a global scale, thus nullifying the broadsword approach. Creating enormous search competition abroad and essentially making standard SEO practices extremely costly in order to maintain effectiveness.

This is where search engine marketing begins. Out of the thousands of visitors that you previously had visiting your website, only a select few were in your ideal target market and actually initiated a conversion on your website site. IE: Purchasing a product online or filling out a contact form for lead generation purposes. No longer cost effectively being able to utilize the broadsword approach and target hundreds of key words for a single website. Search engine marketing, through analysis and research, narrows the scope and pinpoints exactly which search phrases will provide the ideal clientele and highest conversion rates and focuses directly on that.

So what's the difference? Search engine marketing essentially is Search engine optimization refined in order to achieve a more cost effective and customer centric approach to Internet marketing.