sem is more than just adwords...Search Engine Marketing: SEM relates to the purchase of AdWords (or other online marketing media like banner ads). Search engine marketing is very controllable. You decide what you want to spend, which words or phrases you want to purchase, and exactly which page you want your ad to link to.Search Engine Optimization: SEO relates to the examination of a website to find any technical barriers that might be preventing a search engine from accessing a website's content, and then identifying the most relevant site content and improving significant elements (primarily the page's browser title) in order to help the search engine index the content most effectively.
I think SEO is part of SEM because search engine marketing is broader. It doesn't just deal with optimization techniques but branding, and basically getting your website "out there."
Yes you should make your sites for your visitors not for search engine however, building quality related link is a very good way of gaining genuine visitors both directly or through search engine.I focus on getting traffic to my sites and not link building. I have sites for my prospects not for Google.
Search engine marketing refer to online business firm or product selling industries and Search engine optimization is the strategies which help the online business or website.


