A "dropped domain" is a domain that had it's domain registration expire. People buy these expired domains for the cost of registration. Sometimes they are penalized by Google, other times they aren't. It's a real gamble.
Used before and not used anymore. Deleted! If you check at domaintools.com for a domain it will tell you if domain X was used before or not.
okay,thanks for your replies.So bfcb.com.cn is a dropped domain?If i start a new site for this domain,is it still a dropped domain? Can you help with another question?what is a permanet links?I saw many guys selling permanet links,is that mean they are going to keep the site forever?
Having a dropped domain isn't always bad. Dropped domains in the directory business may have negative connotations because sometimes people sell listings based on the PR of the index page. However, if you plan to develop it into a new site with unique and original content, it can be a good thing. A permanent link is a link that remains on a site for the lifetime of that site. So for instance, if you buy a permanent link from someone, they should keep your link up for the lifetime of their site.
You re register/ picked up the dropped domain. It therefore has a history of having belonged to someone before you. Permanent means permanent- some people take it to be the time till which a site exists. Some people define it as a minimum period of 5 years. It is better to clarify with the person from whom you are buying before sealing the deal