Social Networking involves the sharing of interests and information by connecting with other like minded people via the web. Social Networking is all about building lasting relationships.
Micro-blogging tools like Twitter fall under the general category of Social Networking as do popular social bookmarking websites like Technorati, Del.icio.us, Digg and Stumbleupon. On these applications users can add their own keywords (tags) to web pages and blogs.
Social networking is related to social bookmarking: you can make as many bookmarks on the Web as you can possibly stand to do, but once you start sharing these bookmarks with other people, interacting with them, starting conversations through a variety of methodologies, you are networking. You are part of the social networking community.
Social Networking can be used to accomplish serious goals, such as increasing your visibility and raising brand awareness.