The DNS server address(es) currently configured on your computer identifies the first DNS server(s) from which your computer requests each particular DNS lookup. If that server does not know the answer, it will go to other DNS servers until it finds a server that has the particular entry cached. For rarely accessed domains, the requests may ripple all the way through until they reach the DNS server that holds the definitive record.

Along with the record when it is found will be a TTL (Time To Live) value for the record. This says how long the record may remain cached in a secondary DNS server before it has to be fetched again from a definitive record. The record on the definitive server for a particular site will not expire.

For many computers on a home network, their DNS server is their own router, which gets its DNS lookup requests satisfied as the next step by a server in the ISP.

You are not forced to use the router’s or the ISP’s DNS servers. You can use public servers such as Google’s on 8.8.8.8 and 8.8.4.4.

If you do not use the router as your PC’s server then URLs such as ‘http://routerlogin.net’ may not work. These rely on the router intercepting specific names such as this and supplying its own local IP address of your router so that you can log in and configure router settings.