Tom is having issues with Google's DNS server not responding. DNS is the phone book for the internet. It takes the URL and converts it to the unique IP address for that website. It will look in local memory first, then the router, and then the Internet Service Provider for the address. It can even go beyond that to the master servers that house all domain names and DNS lookups. If it can't find it, you get an error message that there's a kink in the chain. That could mean there's something broken on your PC, or even your ISP's servers.
It may also be that his router's settings are messed up. He can try resetting them.