What is the difference between Social bookmarking, Article and Directories?

Hi Can anyone tell me the difference between Social bookmarking, Article and Directories.

Directory allow only 250 characters and bookmarking site allow 1000 characters something.
80% Directory have 0 to 2 PR but social bookmarking site have good PR minimum 3
70% are no follow but 90% social bookmarking site do follow
google daily visit on bookmarking site not in directory

Rtff!!!!

directories contain the website title and a little description

article marketing contain entire articles with a link to your site

social bookmarking sites are based on community recommendations. They usually have nofollow links, but may drive good traffic to your site. Also, google MAY count those link as votes even if they are nofollow.

Social Bookmarking websites : These websites allows you to submit the URL of your page with informative content worth sharing with your audience. If audience finds your content valuable they will bookmark it.

Article Directories : These websites allows you to submit and publish your content on these websites for sharing. The difference between bookmarking sites and article directories is that Social bookmarking websites highlight your titles and when user clicks on them, he will be redirected to your website. Whereas, Article directories publish your content.

Web directories : Website directories allows you to submit your website to these directories, so that visitors come and surf for different websites withing the category. For instance, I want some information about SEO companies... I will go the directors, choose the category and select the website from the huge list.

I was going to ask something similar to this, thanks for the help guys.