Search Engine Optimization (SEO)Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines. Usually, the earlier a site is presented in the search results, or the higher it “ranks,” the more searchers will visit that site. The leading search engines, Google, Yahoo! and Microsoft, use crawlers to find pages for their algorithmic search results.

Search engine marketing, or SEM, is a form of Internet marketing that seeks to promote websites by increasing their visibility in search engine result pages (SERPs). According to the Search Engine Marketing Professionals Organization, SEM methods include: search engine optimization (or SEO), paid placement, and paid inclusion.

One Important Thing To Ponder !

No SEM campaign is complete without SEO. Moreover, 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.

SEM - Search Engine Marketing

This is the process of marketing a Web site via search engines through multiple tactics both paid and organic to increase visibility, brand awareness, traffic and most definitely ROI. SEM encompasses SEO, paid advertising, Social Media Marketing, Blog marketing and Web analytics. Let’s break these down separately.

SEO - Search Engine Optimization

A crucial component of any SEM campaign, SEO is a long term strategy that includes using both on and off page factors such as strategic linking, content, addressing site structure / navigation, and technical search friendliness issues. SEO does not happen overnight. But with a little elbow grease your Web site can enjoy quality targeted traffic and top search positions.

SEO requires content providers to deal with titles, meta tags, html coding as well as keyword density.
SEM involves the use of paid subscriptions, article directories and submitting content in search engines.
Pay per click is another SEM technique used by search engines and website owners to generate traffic for websites. In this case, payment is made per every click of the advertisement.

SEO: SEO is the process of tailoring a website (text, titles, meta tags, alt tags etc...) so that search engines will assign a good rank to the sites for the specific search terms.earch engines introducing fees for guaranteed inclusion in their indices, directories charging for reviews and the emergence of PPC listings, SEO now has an element of media buying mixed in.

SEM: The SEM is meant to be both a tutorial and a general information resource.If you frequent other prominent SEM resources you will find that this tutorial, like most search engine promotion sites, tends to go over the same ground. This is because there are no secrets to successful search engine positioning - just experience, a lot of research and tons of hard work.

seo refers to search engine optimization and sem refers to search engine marketing
seo deals with meta, tagstitles, html coding, keyword & etc.........
SEM ideals with article directories, submitting content,paid subscriptions & etc.......

After all of those years of doing SEO and SEM, I would like to think that SEO is under SEM or just a branch of it. Marketing online also needs some SEO stuff. SEM cannot exist without seo for me but seo can exist with SEM. I like to see those as compiling all of the elements of the website together for the best marketing or for the best ROIs.