I took it for granted that people implicitly understood the difference between Search Engine Marketing and Search Engine Optimization. However, I had to change my thinking when, in a meeting, I got asked this very question; what's the difference?

In my view the root of the answer lies in the early days of the Search Engines. We did not have the Google AdWords and AdSense or the MSN AdCenter or Overture. What we had were Search Engines and the art of making it to the top of the pile was a very technical one, hence the phrase Search Engine Optimization.

Search Engine Optimization by definition is therefore a mostly technical skill which revolves around ensuring that what we code, how we code, ensures that our site appears as high on the search rankings as possible for our given keyword or key phrases.

The landscape changed quite dramatically with the introduction of paid advertising. With products like Adsense and AdWords we now enter the realm of Search Engine Marketing. Advertisers now have the ability to drive their visibility on the search engines right to the top of page one on Google, simply by bidding for their respective keyword.

Search Engine Marketing by definition is therefore no longer a technical skill, but now has all the aspects of marketing a product or service. You are faced with the same questions as you would be if you were marketing in the physical world. Factors like brand, price, positioning and unique selling point become much more important.

A business who wishes to establish an online presence would be silly to ignore the basic fundamentals of Search Optimization even if they have the budget to drive traffic to their site through Search Marketing. My recommendation to any company who are going to create a web presence and intend selling a product is that you need both.

The other question we need to answer is whether the two are mutually exclusive, inclusive or is there some overlap? There is a definite overlap between the two and the easiest way to look at this is the "keyword" link. In classic Search Optimization one would optimize based on selected keywords which one wants to rank for. Often use would be made of tools such as Keyword Density Analyzers to determine what percentage of total text does a specific keyword or phrase take up.

In Search Marketing we still focus heavily on keywords, since we need to bid for those same keywords in terms of our online advertising. In fact the entire keyword scenario moves up a gear as we try to uncover a broader base of keywords that will bring in targeted traffic at a reduced cost per click. The key to Search Marketing becomes exploiting the "long tail of search", which refers to the larger selection of less frequently searched terms.