Online marketing strategy for increasing a site's relevance

Online Marketing

Search engine optimization (SEO)...

... is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "natural") search results. Usually, the earlier a site is presented in the search results or the higher it "ranks", the more searchers will visit that site. SEO can also target different kinds of search, including image search, local search, and industry-specific vertical search engines.
As a marketing strategy for increasing a site's relevance, SEO considers how search algorithms work and what people search for. SEO efforts may involve a site's coding, presentation, and structure, as well as fixing problems that could prevent search engine indexing programs from fully spidering a site.
Search engine optimizers may offer SEO as a stand-alone service or as a part of a broader marketing campaign. Because effective SEO may require changes to the HTML source code of a site, SEO tactics may be incorporated into web site development and design. The term "search engine friendly" may be used to describe web site designs, menus, content management systems and shopping carts that are easy to optimize.

Pay per click (PPC)...

... is an advertising model used on websites, advertising networks, and search engines where advertisers only pay when a user actually clicks on an ad to visit the advertiser's website. Advertisers bid on keywords they believe their target market would type in the search bar when they are looking for a product or service. When a user types a keyword query matching the advertiser's keyword list, the advertiser's ad may appear on the search results page. These ads are called a "Sponsored link" or "sponsored ads" and appear next to, and sometimes, above the natural or organic results on the page. The advertiser pays only when the user clicks on the ad. Pay per click advertising is a search engine marketing technique.
Pay per click ads may also appear on content network websites. In this case, ad networks such as Google Adsense and Yahoo! Publisher Network attempt to provide ads that are relevant to the content of the page where they appear, and no search function is involved.
While many companies exist in this space, Google AdWords, Yahoo! Search Marketing, and MSN adCenter are the largest network operators as of 2007. Depending on the search engine, minimum prices per click start at US$0.01 (up to US$0.50). Very popular search terms can cost much more on popular engines.
Email marketing is a form of direct marketing which uses electronic mail as a means of communicating commercial or fundraising messages to an audience. In its broadest sense, every email sent to a potential or current customer could be considered email marketing. However, the term is usually used to refer to:

Sending emails with the purpose of enhancing the relationship of a merchant with its current or old customers and to encourage customer loyalty and repeat business.
Sending emails with the purpose of acquiring new customers or convincing old customers to buy something immediately.
Adding advertisements in emails sent by other companies to their customers

Affiliate marketing...

... is a method of promoting web businesses (merchants/advertisers) in which an affiliate (publisher) is rewarded for every visitor, subscriber, customer, and/or sale provided through his/her efforts.
Affiliate marketing is also the name of the industry where a number of different types of companies and individuals are performing this form of internet marketing, including affiliate networks, affiliate management companies and in-house affiliate managers, specialized 3rd party vendors and various types of affiliates/publishers who utilize a number of different methods to advertise the products and services of their merchant/advertiser partners.
Affiliate marketing overlaps with other internet marketing methods to some degree, because affiliates are using the same methods as most of the merchants themselves do. Those methods include organic search engine optimization, paid search engine marketing, email marketing and to some degree display advertising.
Affiliate marketing - using one site to drive traffic to another - is the stepchild of online marketing. While search engines, e-mail and RSS capture much of the attention of online retailers, affiliate marketing, despite lineage that goes back almost to the beginning of online retailing, carries a much lower profile. Yet affiliates continue to play a fundamental role in e-retailers' marketing strategies.