SEO (Search Engine Optimisation)

Search engine optimization (SEO) is the process of improving the visibility of a website or a web page in search engines' "natural," or un-paid ("organic" or "algorithmic"), 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,[1] news search and industry-specific vertical search engines.

http://en.wikipedia.org/wiki/Search_engine_optimization 

In my own words.. 

SEO Techniques:

Linking to external sites that have the same topic
Links from external sites to your website
Blogs and forums

When you link an image into a website you include an alternate text tag with in the coding. It is this alternate text tag that the search engines read and display your website in the search list.