Discord is a free voice and text chat app designed specifically for gaming.
The creators describe Discord as follows:
How do i join minr.org Discord?
Head over to discordapp.com/ and download the discord app (recommended) alternatively you can use a browser. Ensure that you sign up to discord as our channel only accepts registered members. Once your have registered your account and logged in with either the app or browser version. Visit www.minr.org/discord this will send out an invite to your account and will allow you to join our channel.
We have our minecraft server directly linked to our discord channel allowing you to keep tabs on the server whilst away. You can also download the discord app or iphone or android!
To link Discord with our server type /discord verify whilst in game and follow the instructions.