What is IPv6
An IPv4 address is a 32-bit number, such as 172.16.254.1. There are (around 4.3 billion) unique IPv4 addresses, a large proportion of which is already deployed.
An IPv6 address is a 128-bit number, written in hexadecimal notation, such as
fc3b:0db8:85a3:0042:1000:8a2e:0370:7334. There are 2128 (around 340 trillion trillion trillion, or ~1038) unique IPv6 addresses.
The massive pool of IPv6 addresses will enable growth of the Internet well into the future.
Read or download (PDF): Netnod Fact Sheet - What is the IPv6?