I'm going to pretty much copy/paste the technet article. If you want clarification on part of it, ask away
The ipconfig /displaydns command provides you with a means to view the contents of the DNS client resolver cache, which includes entries preloaded from the local Hosts file, as well as any recently obtained resource records for name queries resolved by the system. This information is used by the DNS Client service to quickly resolve frequently queried names before it queries its configured DNS servers.