Directory submission in SEO is actually the most easiest and one of the difficult thing to be done as part of on page optimization activity. This largely means that you need to submit your web site url with a brief description and title of your web site. This helps in two ways – provides back link, which the search engines like to see and when ever a user puts a query – search engine’s attempt to check for results in directory and link of a directory is like a vote cast. Hence Directory submission benefits SEO.( this link to go to article section – there is a write up on this subject).