Internet Protocol version 6 (IPv6) is currently the latest version of the Internet protocol. It was originally created to replace IPv4 due to the practical limitation of IPv4 addresses. However, it is not backwards compatible, meaning that networks using IPv6 cannot innately access IPv4 without the usage of some form of tunneling or translation service that can map IPv6 to IPv4 addresses.
The Internet in its current form was designed around IPv4. As such, it is still in use in the majority of networks. While the telecommunications industry will likely see an eventual full transition to IPv6, at the current time IPv6 is not necessary to access services across the Internet.