Many online users are confused between Search Engine Optimization (SEO) and Search Engine Marketing (SEM).
SEO is a way of optimizing your website through the use of meta tags, title tag and contents of the website to get good listing on organic search engine results, in major search engines like Google, Yahoo!, or MSN.
Search engine uses a system known as 'spider' to crawl out data from the website to determine how relevant the website content is to the keyword search. There are various factors, such as content, the relevance of websites back linking to your site and your meta tags, which will determine how your website will be ranked.
However, there is a no guarantee way of getting listed top in search engine results and it takes time and effort to make sure that the linking and content is suitable. This usually takes months to be effective provided that you really understand how the search engine determines their organic result ranking.
SEM is a form of marketing online through search engines' like Yahoo!, Google and MSN. It is a form of paid advertising which can guarantee you prominent ranking on the search engine results. You can choose the keywords that you wish to get listed on. There is no limitation as long as the keywords are approved by the various search engine editorials.
SEM not only includes search but also banner advertising. It is a great way to create online awareness.
Although SEO and SEM serve almost the same purpose, it is always recommended to have both working for you to achieve maximum results. SEO shows you how relevant you can be on organic listing while SEM makes sure you are top always.