Search engine optimized web site.
Means it's optimized for search engine to get a better search result.
Here is a good list of information to help you with
SEO for a new site.
Site Factors
Site URL - Include the keywords in the URL but keep it short!
Site maps - Include a sitemap
Site navigation - Navigation links should be text links and include keyword
Site structure - Allow access to any page in two clicks
URL length - Keep URLs to less than 100 characters
Age of site - Sites that have existed for a long time are favored
Size of site - Add lots of quality content
Unique IP address - It is better to have your site on a unique dedicated IP
Meta tags
Site title tag - Include
SEO keywords at beginning of title
Site description meta tag - Include
SEO keywords in meta description field
Site keywords meta tag - Include
SEO keywords in meta keywords
HTML tags
H1 header - Include
SEO keywords in H1 header
H2 header - Include
SEO keywords in H2 header
Body text
Keyword density - Ensure that
SEO keyword shows up in body text, no more than 5% density
Keyword style - Bold, italics, underlined
Keyword prominence - Keywords at the top count more
Keyword stemming - Include related keywords
Images
Image alt text - Include
SEO keywords in alt text
Internal linking
Use text links - Include
SEO keyword in anchor text
Cross-linking - Have links from your internal sites to other sites
On topic cross linking - Have links from topic pages to sub-topic pages
Outbound linking
Quality links - Link to quality, authority, on topic sites
Text links - Always use text links
Page content
Keep pages fresh - Ensure that page is updated, new content is added
Keep site fresh - Add new content and pages over time