"Quora A continually improving collection of questions and answers created, edited, and organized by everyone who uses it." is a continually improving collection of questions and answers created, edited, and organized by everyone who uses it. The most important thing is to have each question page become the best possible resource for someone who wants to know about the question.One way you can think of it is as a cache for the research that people do looking things up on the web and asking other people. Eventually, when you see a link to a question page on Quora, your feeling should be: "Oh, great! That's going to have all the information I want about that." It's also a place where new stuff--that no one has written about yet--can get pulled onto the web.
Accumulating Knowledge
People use Quora to document the world around them. Over time, the database of knowledge should grow and grow until almost everything that anyone wants to know is available in the system. When knowledge is put into Quora, it is there forever to be shared with anyone in the future who is interested.
Reusable
Each question page on Quora is a reusable resource that should help everyone who has the question that the page is about. Answers on question pages don't depend on any context about the asker except for what is specified in the question text and details. There is only one version of each distinct question on the site, so everyone who is interested in or knows about that material is focused on that one place.
Collaborative
Almost any public space on Quora can be edited by anyone who knows how to improve it. This includes the text of questions and the details around them, what topics are attached to which questions, and the summaries of answers. Quora relies on the good faith of everyone using it to make it a high quality resource.
Continually Improving
People can write their own answers to questions any time they think a question page could become a better resource with more information added to it. People who read question pages rate the different answers so that the best ones can rise to the top of the page and make it better. And people can comment on each other's answers to help them make those better as well.
Organized
People who use Quora keep it organized. Each question has a set of topics attached to it which makes it easier to find questions already on the site. The topics are also used to identify related questions and sometimes give context to a question.
Targeted
People can follow topics so that the system can show them questions they are interested in and know about. People can follow individual questions too, which creates a waiting audience for anyone who wants to write an answer to the question. Some people call this "inverse blogging."
People
Everything on Quora is tied back to a person. Each question and answer has a revision history associated with it, and each change in the log is associated with the person who made it. People use their real names and pictures on Quora and have a short bio describing who they are; this helps anyone reading things they write to understand why they should believe what is written and take into account the author's perspective. For example, if Michael Jordan gives an answer to a question about basketball, that means something really different from someone who has never played the game giving an answer.
source : http://www.quora.com/about/
Naturally, many have questioned its value, but bloggers seem to love it. Is Quora the "biggest blogging innovation in 10 years" as Robert Scoble asks?
As many others have pointed out, Quora has attributes of many other services. You can make comparisons to: Twiter, Facebook, LinkedIn, Wikipedia,Yahoo Answers, Digg, ChaCha...even Google Wave.
