Tailwind Tribes are similar to a group board on Pinterest but better. It's more exclusive, you have to be invited or have a special link invitation to join and you're able to connect with other marketers, bloggers, etc. within your niche.
If you're interested in learning about Tailwind, check out my Ultimate Guide to Using Tailwind for Pinterest here.
Tailwind Tribes are great because they are more niched down than a Pinterest group board and you can get the statistics from the tribes that you're in. Here's an example of the reach and repins that I received from one of my tribes.