Search engine optimization (SEO) is the process of affecting the visibility of a website or a web page in a search engine’s “natural” or un-paid (“organic”) search results. In general, the earlier (or higher ranked on the search results page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engine’s users. SEO may target different kinds of search, including image search, local search, video search, academic search, news search and industry-specific vertical search engines.

As an Internet marketing strategy, SEO considers how search engines work, what people search for, the actual search terms or keywords typed into search engines and which search engines are preferred by their targeted audience. Optimizing a website may involve editing its content, HTML and associated coding to both increase its relevance to specific keywords and to remove barriers to the indexing activities of search engines. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic.

A variety of methods can increase the prominence of a webpage within the search results. Cross linking between pages of the same website to provide more links to most important pages may improve its visibility. Writing content that includes frequently searched keyword phrase, so as to be relevant to a wide variety of search queries will tend to increase traffic.

Updating content so as to keep search engines crawling back frequently can give additional weight to a site. Adding relevant keywords to a web page’s meta data, including the title tag and meta description, will tend to improve the relevancy of a site’s search listings, thus increasing traffic. URL normalization of web pages accessible via multiple urls, using the canonical link element or via 301 redirects can help make sure links to different versions of the url all count towards the page’s link popularity score.

Search Engine Marketing or SEM involves purchasing advertising space from a search engine.  Ads are typically composed of short phrases of text and are triggered by search keywords or phrases.  SEM allows companies’ ads to appear when someone searches for a predetermined search phrase called a “query.”  The ads appear at the top (positions 1-3) and down the right side (positions 4-10) of search results pages.  Each time someone clicks on an ad, the bid amount is billed to the company’s account.

Ad visibility and position is controlled by an automated bidding process, controlled by daily budget and bid per click.  Cost depends on the competition for a particular keyword and the relevance of that keyword to the target webpage.  Each keyword  can have a separate bid which can help drive traffic to a website and increase conversion rates.

PPC ads give companies visibility when their organic rankings do not place them on the first search results page.  One advantage of SEM is that ads can be highly targeted with specific keywords, landing pages, and both demographic and geographic boundaries.