Chat channels are something that will be added in a patch sometime after the initial release. The system will be based around groups, where you will be able to join public channels that are based around your interests. Also the system will include private chat channels (in plans for release in the first few months after the release), where you will be able to connect with your friends.
Awesome news to say the least. With that the issues that fans were begging to be resolved grow smaller.
Links
Battle.net - Source