A good domain name should be simple, short and easy to recall.
It is better to match your domain name exactly like your web address for easy identification and searching. Your domain name may also be a shortened version of the web name or address if it is too long, just like a nickname to a person's full name. In that way, the identification and easy referencing is not lost.
Unless when one is established way ahead of the other and not closely identical as in the case of one domain name but multiple websites, some other special considerations have to be done.