What is IPv6?

From the Wikipedia article:

Internet Protocol version 6 (IPv6) is an Internet Protocol version which is designed to succeed IPv4, the first implementation which is still in dominant use currently. It is an Internet Layer protocol for packet-switched internetworks. The main driving force for the redesign of Internet Protocol is the foreseeable IPv4 address exhaustion. IPv6 was defined in December 1998 by the Internet Engineering Task Force (IETF) with the publication of an Internet standard specification, RFC 2460.