and also Social networking ? Social bookmarking, social networking, social media what is the difference between them? which is the Broader category? and which one 'fits' inside the other? - which one is a sub category of the other? {like Traffic generation fits inside Internet marketing - as a sub category}
Both are not same. Social media represents building your image your credibility like on thousands followers on twitter or fans on facebook. Social bookmarking generally use for link building or these links help your website to get indexed. In nutshell Social Bookmarking is one of the easiest and effective way of link building and you should and must have in your link building strategy.
I completely agree with it and I think this is the main difference between Social Bookmarking and Social Media. Social bookmarking is useful to index the sites quickly and to generate traffic and Social Media is used to build the credibility to the site as you said here.
social bookmarking, blogging, twitter, facebook, linkedin, forums, etc. is all part of the social media umbrella