The Roles of the Title Tag in a Web Pagehttp://www.seologic.com/faq/title-tags.php#roles
Title tags play four roles on the Internet:
1. First, the title is used by resource librarians, directory editors, and other webmasters when they link to your page. If you present editors with a well written title, your site will be reviewed faster and will get favorable treatment by the editors. If you submit a page with a title like this, "Title Tags - Title Tag Limit - Title Tag - Web Page Title - HTML Title Tags," then you can expect to wait for a review.
2. Second, the title is displayed in the search results as the most prominent piece of information available to searchers. Taking the example above, put yourself in the mind set of a search engine user who is scanning the search results. If you see a title like the one above, which is so obviously stuffed with frequently searched keyword phrases, don't you think you would consider that the Webmaster is trying a bit too hard to get your attention, putting search engine optimization far above web usability? We think so.
3. Third, the title is displayed by the visitor's browser (most often Microsoft Internet Explorer) in the border of the viewable screen as the visitor is viewing your website. This serves as an anchor so that the visitor knows where he or she is on your website. For this reason, titles need to clearly relate to their page and should include bread crumb or mouse trail information if there is space available. Microsoft's browser, called Internet Explorer, displays the first 95 characters of your title tag. For title tags longer than 95 characters, Internet Explorer will simply crop the tag, as you can see it has done to the title of this Web page.
4. Fourth, the title is used by the major search engines as the most important piece of information available in order to help them determine the topic of your page, and thus to determine the ranking of your page in their search results. Given that the title is the most important factor in your page's ranking, it can be very tempting to load the title tag with keywords. For the first three reasons mentioned above, you should avoid the temptation.
Basically if you use the title and description tag well you will show up in Google with all those keywords that people can use to find your website.