A domain is the website's name as it appears in the URL.


In the address acebit is the second-level domain and .de the top-level domain.

If it fits in, it can be a good idea to use the main keyword in the domain. But more important than that is that you choose a domain name that isn't too long and that's easy to remember. Often the unique and original domain names are the more successful ones. Think about what would have been if Twitter used online-messages-network or Google used free-search-engine as their domain name. In both cases they would have the keyword in their domain name, but would they also have the same success?