What's the difference between SEO and SEM?

According to me SEM campaign is not complete without SEO. Since the purpose of SEO is to make the site better for both search engines and users, you may find that it will suffice on its own. In any case, the advantages of SEO over the other aspects of SEM make it clear that, even if you are going to spend additional money on advertising and paid placement, SEO must be your first step in promoting your site.

Search engine marketing (SEM) refers to the short text advertisements which generally appear at the top or down the right hand side of search engine results. These are often labelled as "sponsored Links" or "sponsored results". These advertisements are generally purchased from GoogleTM (the Google AdwordsTM product), or Yahoo! Search Marketing (YSM - formerly Overture)TM (YSMTM supplies the paid search advertisements to Yahoo!TM Search, and ninemsn Search, here in Australia).

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all i can say is practice and theory...and we needed both.

Thanks Wincer Song! You have named about a nice book. Seo is the part of SEM. SEM is about the whole marketing process over internet.

Mainly in SEO (search engine optimiziation) they optimizing the vale of keywords that is high rank in Search engine,But SEM (search engine markting) is to markting for a comany to do smo for thair sites.

SEO stands for search engine optimization which is only use for organic search result in search engine. SEM stands for search engine marketing the paid way of online promotion called SEM

"Jane Porterfield" is true she is very right..

Let's start with SEO, as it is a part of SEM. SEO is the act of optimizing the HTML and other content of your website for relevant, targeted key phrases in order to attain higher natural listings than competing websites. SEO provides a cheaper long term solution for increased qualified traffic and generates customer inquiries that ultimately convert to sales.

Now SEM is broader than SEO. It includes SEO and other areas to improve a sites visibility in search engine results pages, like paid list

SEO is simply SEM in normal language! While in the umbrella meaning SEM is marking strategy that follows the term SEO, website to rank higher in search engines..

SEO means search engine optimization. It is a technique of promoting your website in the search engine ranking without paying to search engine. And SEM stands for Search engine marketing. It is also a technique of promoting a website in search engine, but in this you have to pay to the search engine to get visible in search engine position rankings (SERP).

SEO means search engine optimization, SEM equal with search engine marketing procedures.

From Wikipedia:

Search engine marketing (SEM) is a form of Internet marketing that involves the promotion of websites by increasing their visibility in search engine results pages (SERPs) through the use of paid placement, contextual advertising, and paid inclusion. Depending on the context, SEM can be an umbrella term for various means of marketing a website including search engine optimization (SEO), which "optimizes" website content to achieve a higher ranking in search engine results pages

SMO (Social Media Optimization) is basically promoting business through various Social Media channels like Facebook, twitter, tumbler, etc. And in SEO we basically optimize our site for getting higher ranking in SERPs.

The SEO is only one of SEM strategries. I recommended this book to you for learning SEM. "Search Engine Marketing, Inc.: Driving Search Traffic to Your Company's Web Site (2nd Edition)"