An expired domain is domain of which the term was not renewed. Therefore, such domain names are again available on the open market, for example through SEDO (German domain host). They usually have domain trust due to their history, backlinks, and Page Rank.
The three factors, trust, backlinks, and PageRank are the basis for a monetary valuation of expired domains. Other factors are traffic, name, and the market relevance of the domain. An exact determination of the value of a domain is not possible. Supply and demand in the market determine the selling price.
The backlinks may have grown organically over the years and will be judged by Google correspondingly high, which affects the PageRank.
Expired domains are often used for new projects due to their existing backlink structure. The domain topic and language are usually not changed. It may also get utilized with a 301 redirect on your website or project. In the latter situation, the expired domain will continue to lose value from Google’s perspective. Expired domains also get traded.
The locating, registering, and re-selling of expired domains has developed into its own market. A variety of domain traders who specialize in this business model have already established themselves on the Internet. Furthermore, some individuals try to reserve domains once their term is over through the use of scripts.
If you want to reuse an expired domain and have found one through a website such as expireddomains.net, then you should examine the domain in question in detail beforehand because such a fast SEO Booster may prove to be a bad investment.
Another important aspect in the reuse of an expired domain is trademark law because in many cases trademarks are mentioned on expired domains. If it now gets revived with the same content, then the new operator must find out whether he may use the mentioned trademarks again.
In the past, expired domains were used by SEOs to establish their own highly sophisticated link network or to open up new and affordable backlink sources. However, Google is now able to identify such structures and regards them negatively. Therefore, such pages can expect a worsening in ranking or even suffer the removal from the Google index in the future.