"DNS suffixes" are used for resolving unqualified domain names (names with no dots).
In the Windows Control Panel, under "Network and Internet" click the "View network status and tasks" link:
Click the "Manage network connections" link:
Right-click a network connection and select "Properties" from the pop-up menu:
In the network connection Properties dialog select "Internet Protocol Version 4 (TCP/IPv4)" and click the "Properties" button:
In the "Internet Protocol Version 4 (TCP/IPv4) Properties" dialog click the "Advanced..." button:
In the "Advanced TCP/IP Settings" dialog select the "DNS" tab, and specify which DNS suffixes to use for resolving unqualified domain names:
If you choose the first (and default) option to append primary and connection specific DNS suffixes, then you will also need to configure the primary DNS suffix. See reference article below.