IPv6 is the version of the IP protocol designed to substitute the precedent IPv4 standard. IPv6 mainly differentiates by the number of bits assigned, which changes from 32 to 128.
In the last years the problem of the exhaustion of available IPv4 addresses has got more and more important: the choice of 128 bits allows to manage a total of 4,3 x 10^38 addresses. If they were spread on the ground, there would be hundreds of thousands IP addresses per square metre.

The release of the first addresses with the new format by ICANN was on the 4th February, 2008, when they first got recorded into DNS systems. On the 3rd February, 2011, the last IPv4 block was assigned, but it’s estimated that until 2025 IPv4 will be used allowing users and providers to adapt to the new paradigm.