Many times when I read articles and posts involving SEO the writer just uses the term for anything about getting a website listed in the search engines. Sometimes to avoid confusion they'll distinguish between onsite-SEO and offsite SEO. This is further confused by the fact that some backlink building and site promotion is done for the search engines and some is done to get direct traffic. Much of it might be good for both, or some things might work better for one than the other. Originally SEO was only about optimizing the design and content of your website to get a better listing in the search engine, (hence the term Search Engine Optimization). Any backlinks made were simply considered promotion for you're website. That's how it was before Larry Page and Sergey Brin came up with Page Rank and started Google. Once the Google started using how sites linked to each other to determine ranking in the SERPs, then people started discussing site promotion as another aspect of SEO. SEO is used to mean so many different things that it kind of defeats the usefulness of using the term in the first place and causes a lot of unnecessary confusion. In my own posts on various blogs, forums, articles, etc. I've started using more precise terms in order to make it easier for new people to understand what's being discussed. I've noticed a lot of other people doing the same thing. Since there's still a lot of people that don't, I thought I'd make this post to explain the terms which seem to be more explanatory than just referring to everything as SEO. Search Engine Marketing (SEM) This is the overall term for what you're trying to achieve. SEM is everything that's done in order to get you're website listed in the top Search Engine Results Page (SERP). The intention is to use a listing in the SERPs to generate traffic. If you choose SEM as your traffic generation strategy then there's two things you need to take care of... . Search Engine Optimization (SEO) SEO is about content and design. Everything you do when designing your website or page that will optimize it for the search engines is SEO. Choosing a SE friendly design, using keywords in the url and content, using proper tags, unique content for each page, and everything else that you do when originally setting up the website in order to rank in the SERPs. (This is often called onsite-SEO, but that's kind of redundant since SEO originally only applied to onsite or onpage). . Search Engine Promotion (SEP) SEP is about backlinking and site promotion. SEP is what you start after you've done your SEO. This is everything you do to promote you're website in an effort to get found by the search engines. SEP is everything you do to build backlinks to promote your site to the search engines. The quantity and quality of links that the SE finds pointing to you're website will determine how well you rank in the SERPs. (It's often called offsite-SEO, but truly isn't about optimizing but more about promoting). This even applies to things like article marketing. SEO is what you take care of when writing the content of your article, things like keyword density, using tags, etc. SEP is what you take care of when promoting it, things like keywords in the anchor, sites you're backlinking on, etc. (While the content of the article would be SEO, any links within the article would be SEP for the target of the links. The article itself would be considered an SEP factor as it pertains to the main site it's promoting) Any time you're creating backlinks just to improve you're position with the search engines then you're doing SEP, if you're making backlinks with the actual intention of getting visitors from the link then you're doing a Direct Promotion. Most of the time a Direct Promotion link will help for SEP, but a link made just for SEP won't always make a difference for Direct Promotion. So in summary - SEM is your overall plan for your website to get a high rank in the SERPs to get traffic from the search engines. SEO is everything you do onsite or onpage to optimize your website to get a better listing in the search engines. SEP is everything you do offsite or regarding links to promote your site with the intent of getting a better listing in the search engines. It might not seem that important to a lot of people, but I've found it really does make it easier to explain things when those terms are used in that manner.