SEO
Search Engine Optimization is the use of on-page and off-page techniques in the effort to show your website higher in the organic (unpaid) search results.
When you do a search on Google, the first few results in the shaded area at the top and all the results on the right side of the page – are paid ads. Advertisers write the copy and determine the keywords they show for – not Google. The remaining results on the page are not paid but Google’s best guess of the most relevant and authoritative results for your search query. Lot’s of webmasters would like their businesses to be listed here. As a result, the search engine optimization field has developed.
On – Page SEO includes optimizing all page elements so that search engines can easily determine what your site is about. This may include changes to the titles, headlines, body copy, and even the navigation of the site.
Off page SEO includes submitting your website for inclusion in directories or other search engines. Additionally links from other websites with content in related topics can improve the “authority” of your website.
SEM is Search Engine Marketing, ads shown in response to search queries. The primary tool for this is Google AdWords which shows ads in response to searches on Google but also on a network of partner search engines such as AOL.
With SEM you can determine what keyword searches trigger your ads, show only the most relevant of your ads, and choose in what geography. For example, you can schedule ads to show from Nov 1 until Christmas, only in Gainesville and Haymarket VA, and only from noon until 9pm.
Control vs. Influence
This exposes the major difference between SEO and SEM – with SEM, you have control over your marketing. With SEO you can only influence the results.
Pay for Time or Benefit
With SEO you pay for the time and expertise to make the “on page” and “off page” optimization regardless of any benefit. With SEM you will also pay for expertise, but a large component of the fee will be results based – pay per impression or pay per click.
Risk
SEO results vary widely as Google changes the algorithm that determines rank and competition changes. SEO results can come in a few days, take weeks or longer, have long lasting benefit or no benefit. With SEM, ads usually show with a few hours of when they are created. Results are fast and easily measured. Ad copy can be easily changed and multiple ads can be tested against each other. In these respects SEM is far superior to SEO.