IP Number = Internet Protocol Number.

A unique numeric address that is given to servers and users connected to the Internet. IP number consists of 4 parts separated by dots (e.g.165.113.245.2). For servers, it is translated into a domain name (that is easier for people to remember), by a Domain Name Server (DNS). For users, it is assigned by the Internet Service Provider (ISP) when the user goes online. This IP address might be the same number each time you log on (called a static IP), or it might be a newly assigned number each time you connect, based on what's available. Most Internet users prefer the static IP because some Internet telephony programs, for example, such as CUSeeMe, need your current IP address to make a connection.

IPv6 (short for "Internet Protocol Version 6") is the "next generation" protocol designed by the IETF to replace the current version Internet Protocol, IP Version 4 ("IPv4"). Most of today's Internet uses IPv4, which is now nearly twenty years old. IPv4 has been remarkably resilient in spite of its age, but it is beginning to have problems. Most importantly, there is a growing shortage of IPv4 addresses, which are needed by all new machines added to the Internet. IPv6 fixes a number of problems in IPv4, such as the limited number of available IPv4 addresses. It also adds many improvements to IPv4 in areas such as routing and network autoconfiguration. IPv6 is expected to gradually replace IPv4, with the two coexisting for a number of years during a transition period.