The process and strategy of using search engines results as an advertising vehicle. This may include improving rank in organic listings, purchasing paid listings, or a combination of methods all designed to increase visibility, clicks and, of course, leads and orders. Related terms: Conversion rate, Cost per click (CPC), Search engine optimization (SEO)
You need the meaning of SEM ? Did you try to search the forums before posting this thread Anyway, here is a good reading for you my friend: http://en.wikipedia.org/wiki/Search_Engine_Marketing Enjoy