A+ More on IP addresses
IP (Internet Protocol) addresses are 'hierarchical'; like phone numbers, where the area code and the first two digits of the phone number can tell you where the phone number is (like 305 is Miami and 503 is NW Oregon)
(except for numbers which have been Ported, but don't get me started on THAT infernally bad idea).
IP addresses also group and can be identified by the nation and the ISP which issue them, at sites like http://tools.whois.net/whoisbyip.
Every packet of Internet data contains the IP address the packet is supposed to go to, as well as the Software Port it's supposed to arrive at, and the Protocol (ICMP, UDP or TCP) which will use the data.
Popular ports include 20 and 21 for FTP, 23 for Telnet, 25 for SMTP, 53 for DNS (the 'white pages' of the Internet), 67 for SMTP, 80 for HTTP, 110 for POP, 443 for HTTPS, 1863 for the Kinect and 3074 for the Xbox. RFC 1597 outlines the most popular port assignments, and you can see those at iana.org/assignments/port-numbers.
DNS looks up www.whatever and finds an IP address for it, and if it can't find an address, it goes and asks another DNS server.