Direct traffic is the type of website traffic where visitors come to your website directly, without being referred to by search engines or other websites. This type of website traffic also includes personal bookmarks and RSS feeds. Most webmaster pay less attention to direct traffic when running a campaign to increase their overall website's traffic.
Direct traffic visitor is one of the most important type of visitor your website could get. To have specifically chosen to visit your website, it is the most targeted type of website traffic. Direct traffic visitors are also not affected by outside factors such as when there are changes in search engine ranking. They also respond well to you website's offering, and tend to promote your website or content more than the other type of website traffic shall they find anything useful.
Branding is the most important factor in getting direct traffic. Some would directly go to Google for search, CNN for news, and TechRecipes for technical howto (ahem). They have become THE place to go for their niche. Building a brand around your website would definitely increase direct traffic visitors.
There are just too many websites in existence in the Internet nowadays. To stand out from the crowd, your website should excel it what it aims to do. For example, from the many websites that provide technical howto in the Internet, TechRecipes try to be the one with the most accurate and detailed.
To attract repeat and direct traffic visitors, your website should be memorable in a good way. This includes easy to remember URL, good design, etcetera. People don't always like to visit cluttered website over and over again.